Stephen Strasburg and Early Season Velocities

With the real Opening Day behind us — sorry Astros and Yankees, you’re just late — we now have real 2014 data from almost every team on the leaderboards. Of course, besides answering trivia questions, we all know that there’s really nothing insightful to be learned from one day’s performance, and we’re not going to find useful information to be analyzed there until the samples get a lot bigger.

But there are some numbers that became useful in very short order. Strikeout rate, for instance, only has to be regressed 50% to the mean at a much lower number of batters faced than most other pitching metrics, and big changes in K% over even a few starts can prove somewhat meaningful. It’s hard to fluke your way into getting a bunch of Major League hitters to swing through your pitches, and if you’re consistently throwing pitches by people, it’s a pretty good sign for the future.

That’s still a results-based metric, though, and by definition, those have to include significantly more variables than things that do not require a response from either the opposition or the teammate. The things that we can measure the quickest are the things that are affected by as few players as possible, and ideally, only one player. For instance, a catcher’s caught stealing rate will take more time to tell us about his arm strength than simply measuring his pop time — baseball lingo for the length of time it takes him to throw down to a base on a steal attempt — because CS% also includes the pitcher and the runner as variables. With enough CS attempts, we can infer things about a catcher’s arm strength from the results, but if we have pop time, we can measure that arm strength directly, and do so much faster.

That’s one of the reasons why we love PITCHF/x data, and specifically, the velocity readings they give us. We can infer quality of stuff from strikeout rate — guys who throw hard get more whiffs, generally — or swinging strike rate, but we don’t have to anymore, since there’s a direct measurement that takes place for every pitch of every Major League game. Velocity readings don’t care about quality of opposition or the umpire’s strike zone that day, with the pitcher himself being responsible for almost 100% of the calculation. Ballpark effects — the system is not calibrated exactly the same in every single city, and there are parks that run a little “hot” or “cold” — and weather have some impact, but relative to other metrics, the outside factors have very little impact on a pitcher’s velocity readings.

How quickly do fastball rates mean something? Jeff Zimmerman noted that a starting pitcher’s velocity over three starts will usually be within 1 mph of his seasonal average velocity. Not surprisingly, velocity can be meaningful very quickly. If any stat from the first day of the season means anything, it’s probably fastball velocity. But, even knowing that, we still have to use caution when trying to draw any kind of strong conclusion from limited samples of data.

For instance, you’ve probably read today about Stephen Strasburg‘s lower Opening Day velocity; his pitches that were classified as four seam fastballs averaged just 92.7 mph, down from 95.2 mph a year ago. When asked about it after the game, Strasburg said this.

“It felt pretty good. I guess radar guns have offseasons, too. I don’t know,”

The nice thing about PITCHF/x is that the cameras don’t have to get into game shape, and there usually aren’t gross measurements errors. But that doesn’t mean the system is perfect either, so when you see a pitcher post a significantly different velocity than you’re used to, the first thing I’d suggest doing is checking the velocities of every other pitcher in the game too. If the system is producing a systematic bias, it will show up in the other pitcher’s numbers, and should be easy to spot.

Yesterday, Strasburg was opposed by Dillon Gee of the Mets, and the same system that clocked Strasburg’s fastball down a few ticks had Gee sitting at 88.3 mph with his four seam fastball, a 1 mph decline from his 2013 average. So, immediately, we know we should keep investigating, because the first flag for systematic PITCHF/x calibration error has been raised. So, let’s go to the relievers who recorded at least three outs (and pitched significant innings in the majors last year), although with the qualification that now we’re taking small sample data even smaller, as we’re looking at 10-30 pitches in most cases.

Bobby Parnell: 92.8 mph yesterday, 95.1 mph last year
Jose Valverde: 91.9 mph yesterday, 92.8 mph last year
Tyler Clippard: 92.4 mph yesterday, 92.0 mph last year
Drew Storen: 92.0 mph yeserday, 93.7 mph last year
Jerry Blevins: 88.7 mph yesterday, 89.8 mph last year

Outside of Tyler Clippard, everyone was down yesterday, and Bobby Parnell had as big a drop as Strasburg. That would normally be encouraging, as it would be a decent indicator of the system in New York just running a bit slow, except as I write this, the Mets just announced that Parnell was pitching with a partial tear in his MCL, and he’s headed to the disabled list. So, yeah, that explains Parnell’s velocity drop.

But, keep in mind, Parnell isn’t the only guy who threw yesterday and had lower than last year’s average readings, and they aren’t all headed for surgery. And that’s because it’s April, and velocity is at its lowest point in the first month of the season. Last year, by month, average four seam velocity from PITCHF/x:

April: 91.5
May: 91.6
June: 92.0
July: 92.2
August: 92.2
September: 92.3

Comparing April velocity to seasonal average velocity will often make it look like a pitcher’s not throwing as hard, because pitchers just don’t throw as hard at the beginning of the year as they do at the end of the year. Instead, what you want to do is compare a pitcher’s velocity from this year to the same time period last year. And, while we haven’t advertised this feature enough, you can actually do that right from our game logs.

For instance, here is Stephen Strasburg’s game log for the last 365 days, in chronological order. You can see the huge cliff between his final start velocity of 2013 and his first start velocity of 2014, but you can also go back and see what his numbers were on Opening Day last year. In this case, they’re not particularly encouraging, because Strasburg’s four seam fastball sat at 96.0 last year, the highest average he’d post all year. But, it was still worth checking, and often, you will see that the difference in a pitcher’s velocity from the same time period last year will be less than the difference between his early starts and his seasonal average from the year before.

Also, it’s worth keeping in mind that nearly every pitcher loses velocity as they age. Strasburg throwing slower shouldn’t actually be a shock; it would be a surprise if he wasn’t ticking downwards. This is just how pitcher’s age. Throwing hard is a young man’s game, which is why a 21-year-old was the hardest throwing starter in MLB yesterday. Velocity peaks incredibly early, and it is unlikely that Strasburg will ever throw as hard as he used to. That’s not necessarily a sign of injury; it’s a sign of Strasburg being older.

Now, it can be a sign of injury, as Parnell’s MCL tear shows. Lowered velocity does have a correlation with higher injury rates, and it is an early warning sign that something might be wrong. But before you draw too many conclusions from early season velocity readings, remember that park effects do exist on these readings, and that April velocities are often lower than seasonal averages. Use the tools available to check and see if a park was running hot or cold on a given day. Use the game logs to see how a pitcher’s velocity changed throughout prior seasons. And don’t overreact to one start.

Stephen Strasburg’s missing velocity might be something to worry about. Or it might be nothing. As we know with every other metric, one day’s numbers mean basically nothing. That’s less true for fastball velocity, but it’s still mostly true. Let’s give it a few more starts, and if Strasburg is still sitting at 93, then we can start to wonder what that kind of change might mean for the future.

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Dave is the Managing Editor of FanGraphs.

42 Responses to “Stephen Strasburg and Early Season Velocities”

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  1. Keegs says:

    I went to the game yesterday and it was very, very cold. It got up to 50 near the end but sat in the low and mid-40’s while Strasburg was still in. There were snow showers in the AM, and it was very windy all day. The on-screen radar gun was broken for the first 7 innings, so we never saw a number for Stephen, but my buddy and I (both Nats diehards) could tell Stras never got truly warm.

    Barrett was throwing heat though.

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    • Dan Rozenson says:

      Last year’s opening day was in the 50s — not exactly balmy. The PITCHf/x velo readings seemed fairly true to me and I didn’t notice any other systemic errors in the data.

      Another thing about Stras was that his fastball was about average for last year in the first inning, but dipped after that.

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      • Cool Lester Smooth says:

        So, what you’re saying is, that last year the temperature was 10 degrees warmer than it was this year?

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      • pft says:

        Velocity readings park to park at any given time can be as much as 2 mph difference from high to low. That’s why they say +/-1 mph when they talk about the accuracy for the pitch f/x system.

        Over 3 starts things should smooth out

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    • Travis L says:

      Has anyone done a study that correlates game time temperature with velocity, or do we assume that cold weather causes pitchers to throw slower? (I’m excluding the month-by-month velocity information because that contains a number of other factors.)

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    • Mat says:

      If you and your buddy (both Nats diehards) could “tell that he never got warm” guess we can get rid of PITCHF/x.

      Over/under on 600 Ks for Strasburg. You taking the over?

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      • …do you think that Pitch F/X tells us if a pitcher has ward up properly?

        That’s something that only people who watch a pitcher regularly, such as Nats diehards in Strasburg’s case, can be expected to recognize.

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      • Curtiss says:

        Well given that 600Ks would be 3 Ks an inning for 200 innings I think that anybody would take the under. I think a fairer break point would be 1 strikeout per inning, and I feel pretty safe in saying over on that.

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  2. Derek says:

    It is also noteworthy that Strasburg struck out 10 in 6 IP yesterday.

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    • vivalajeter says:

      *Against the Mets.

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    • Luke in MN says:

      Right, and is it actually true that velocity is a better small-sample indicator than K% or swing-and-miss%? A pitcher might be trading velocity for movement, e.g. It’s an empirical question and I get the sense that the article is assuming the answer without really knowing.

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  3. emdash says:

    I wonder if some of the pitches were mistagged – he threw a (not very good) slider several times that didn’t move very much, so it seems possible that the lack of movement could have it identified by the system as a fastball instead. That would pull down the average, at least.

    Not sure why he’s so committed to the new pitch – hopefully it was just a function of facing the Mets in Spring Training right before the season and wanting to have something different to show them, but it’s hard to say.

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    • Paul Clarke says:

      There was definitely some mistagging by Pitch F/X, but it doesn’t look like any of the sliders got classified as fastballs. Instead the faster ones were called changeups and the slower ones curveballs. It also looks like some of the slower fastballs (probably two-seamers) were classified as changeups, so the actual fastball speed was probably a bit lower than Pitch F/X says.

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  4. Paul Nicholas says:

    I disagree. You say four seam fastballs? I think FA is “unclassified fastball”. His 2 seam fastball avg 94 mph and is 1mph slower than previous years.

    How’d he do in Spring? I would look at those velocities, too. Google should find something on that. I wouldn’t read much into the first game of the year. I wouldn’t be surprised if weather was an issue. 10Ks is a good sign. The Nats wouldn’t leave him out there for 6IP if he wasn’t right.

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    • cass says:

      FA is specifically four-seam fastball in the pitch-fx numbers.

      Also, the slider was not mediocre. He struck out two batters with it, including David Wright in the 5th. No one made contact with the slider. It was misclassified as a change-up cause the pitch-fx recognition software hasn’t been updated for Strasburg, but if you go to, you can see it clearly.

      Or just pull up video of the Wright strikeout in the 5th. Strasburg used a fastball, change-up, curveball, and slider against Write, so it’s easy to compare them all.

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  5. Paul Nicholas says:

    *includes unclassified FB

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  6. bvillebaron says:

    Well maybe 4 earned over 6 will slow the Strasburg hype train at least until his next start.

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    • cass says:

      You apparently are still living in 2010. There’s no Strasburg hype train anymore.

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      • Pennsy says:

        I have seen him here and there bandied about as a Cy Young winner this year. The hype will stay with Strasburg until he has a real clunker of a season, then people will move on to the next shiny toy.

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        • arc says:

          He has a career ERA- of 78, a career FIP- of 73, and a career SIERA of 2.78. Those are Cliff Lee numbers over the last 3 years – except he’s 25. The hype has been warranted.

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  7. Stan "The Boy" Taylor says:

    “Parnell isn’t the only guy who threw yesterday and had lower than last year’s average readings, and they aren’t all headed for surgery.”

    For once, I disagree Dave. They are all pitchers, so they are all headed for surgery at some point :)

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  8. Dr. K says:

    Strasburg has been talking about refining his game and pitching more to contact. I assume the point is to not waste 8 pitches on a number 8 hitter or on some AAA no-name like Andrew Brown (no offense, Andrew).

    I would guess that that change of approach was at play when he grooved the fastball to Brown. Obviously Strasburg is still working out the kinks, but I think the point is to be a more well rounded pitcher, like a Wainwright, with the understanding that his stuff will lose something with age.

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    • cass says:

      He said he was trying to pitch to contact when he made his debut and struck out 14. Every year he says he’s working on pitching to contact more. Now, last year he actually made good on this and upped his GB% while lowering his K%, but Nats pitchers generally talk about how they’re not trying to strike people out.

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  9. Natty says:

    Brooks’ data has his FB avg at 93.6 with max at 95.8. Looks like he was still nearly touching 95 between his 96th and 100 pitches too so a lot less worrisome than saying his FB averaged 92.7 for the game.

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    • gabrielthursday says:

      Yep, Dave needed to check Brooks before writing this. Brooks is just much better at classifying pitches, at least initially.

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      • gabrielthursday says:

        Okay, I think I need to apologise to Dave. I gather Brooks scales up velocity a little bit to represent the velocity at 55 feet from the plate (rather than 50). Brooks has Strasburg’s velocity last season at 96.1, so Dave used the correct apples to apples comparison.

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  10. Ted says:

    Anybody notice Cliff Lee yesterday? He was pitching 89-90 so according to Brooks and data here hes down about 1.5-2 mph. Fact that he got clobbered for 8 runs and he’s not exactly a young buck, this could be a VERY bad sign for us owners…

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    • cass says:

      Well, it’s not a terribly bad sign for his actual owners since the Phillies can lose without him just as easily as they can lose with him.

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  11. Eddie says:

    Check out Sonny Gray last night. His FB was averaging only 91, well below his numbers from last year.

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  12. pft says:

    That big a drop in velocity is a sure indicator that something is not right physically, labrum, rotator cuff, UCL, TOC, who knows. They don’t always have pain as a symptom

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    • snack man says:

      It could also be a strain or that the slider is wearing him out and he’ll have a shitty first half followed by dropping the slider and recovering his form (or not realizing it’s the slider and imploding completely).

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  13. robertobeers says:

    Nobody wants to mention velocity gainers? Brandon McCarthy is up over 2 MPH on his sinker and 1.5 MPH on his cutter. He also exceeded his fastest career pitch speed by 1.3 MPH.


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  14. CC Sabathia says:

    Where’s my article?

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  15. bvillebaron says:


    Get back to me when Strasburg pitches 200 plus innings in a season and wins a Cy Young okay. Never said he wasn’t a very good pitcher, but he sure ain’t Clayton Kershaw.

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    • nada says:

      High bar much? Not every player who wins a Cy Young has won a Cy Young before.

      Strasburg is good and young, which is to say there’s reason to think he could have a great season. You can call that hype, I’ll call it ‘projection’.

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    • cass says:

      Did someone say he was Clayton Kershaw?

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  16. Derek says:

    It is also noteworthy that this was Strasburg’s first start after offseason elbow surgery (removed bone chips). That fact can cut both ways. On the one hand, we might expect that a pitcher coming back from elbow surgery to have a velocity dip before getting back to normal levels. On the other hand, the surgery itself could be the cause of a permanent loss in velocity.

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  17. Derrick says:

    Strasburg’s velocity was almost all the way back during his 2nd start.

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  18. hscer says:

    I think he’s fine.

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