Jered Weaver’s K Rate

Though the Los Angeles Angels of Anaheim have played .500 ball to this point and have a run differential (negative 26) that suggests they’ve been lucky to break even, you can’t blame Jered Weaver. The 27-year-old righty, selected out of Long Beach State with the 12th pick in the 2004 draft, is turning in the best season of his major league career.

In 75.2 innings pitched, Weaver boasts a 3.40 expected FIP (xFIP) that places him sixth in the American League among starters tossing at least 50 frames. Weaver is displaying customarily sharp control, issuing 2.5 free passes per nine innings and getting ahead in the count with a 60.1 first pitch strike percentage (58% MLB average). But the biggest reason for his lights-out pitching is a large increase in whiffs.

Weaver is getting swinging strikes 11.3% of the time in 2010, well above his career 9.4% mark and the 8-9% big league average. His overall contact rate is 75.1%, besting his 78.8% career clip and the 80-81% MLB average. On a related note, Weaver is getting hitters to expand their zones more often, with a 31.6 Outside Swing% (27.3% career average, 25-27% MLB average in recent years).

Consequently, Weaver’s K rate has climbed:

Heading into 2010, Weaver had 7.32 K/9 during his career. CHONE predicted 7.25 K/9 for him this year, and ZiPS 7.1 K/9. After an eight punch out performance against the Royals yesterday, Weaver now has 9.87 K/9 on the season. That’s second among AL starters, behind only Toronto’s Brandon Morrow. But Weaver has actually K’d more on a per-plate appearance basis: Jered has a 27.1 K%/PA, compared to 26.1% for the control-challenged Morrow (those extra free passes extend the inning and give him more chances to whiff batters).

So, is Weaver doing anything different this year? Here’s his pitch selection over the 2009 and 2010 seasons (data from Trip Somers’ texasleaguers site):

Jered’s four-seamer is a tick quicker, and his whiff rate with the pitch has gone from below the six percent big league average to a robust 9.3%. He has added a two-seamer to his repertoire, which may help explain his (relative) rise in ground balls (37.8 GB%, compared to a career 32.9 GB%). The whiff rate on his slider has increased considerably (from 12.2% to 17.3%), though his curve’s rate of whiffs has declined (12.7% in ’09 and 9.3% this year).

Weaver hasn’t thrown his changeup as much this season, but when he does, he’s still getting a ton of swings and whiffs. The relative difference in velocity between his four-seam fastball and change has increased — there was an 8.3 MPH gap in ’09, but an 11.6 MPH split in 2010.

There’s also a change in terms of the relationship of horizontal movement between the two pitches. In 2009, Weaver’s four-seamer had 3.3 inches of movement in on the hands of right-handed batters, while his change had 5.7 inches of movement away from lefty batters (a 2.4 inch difference). In 2010, Weaver’s four-seamer has 1.4 inches of horizontal movement, and his change has 6.8 inches (5.4 inch difference). For reference, the average difference in horizontal movement between four-seamers and changeups (per Somers’ site) is about half an inch.

Perhaps that big gap in movement, coupled with the introduction of the two-seamer (which has similar horizontal movement as the change), is flummoxing hitters. According to our Pitch Type Run Values, Weaver’s fastball/change combo is faring better than ever: his fastball has been worth +0.64 runs per 100 pitches thrown (+0.07 runs/100 career) and his changeup has been +2.79 per 100 tosses (+1.38 career).

Is Weaver’s increased K rate to be believed? To an extent. Strikeout rate per plate appearance for pitchers tends to become reliable around 150 batters faced, and Weaver has taken on 306 hitters so far this season.

The change is Weaver’s whiffs is reflected in his rest-of-season ZiPS projection — the ROS ZiPS are so helpful because they incorporate a player’s performance during the current season, giving us a more accurate reflection of his talents. ZiPS projects Weaver for about 7.8 K/9 for the rest of 2010, compared to the system’s 7.1 K/9 pre-season forecast. While Weaver isn’t likely to keep whiffing well over a batter per inning, his increase in K’s should not be written off as a total fluke. Odds are, he’ll keep some of the gains that he has made.

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A recent graduate of Duquesne University, David Golebiewski is a contributing writer for Fangraphs, The Pittsburgh Sports Report and Baseball Analytics. His work for Inside Edge Scouting Services has appeared on and, and he was a fantasy baseball columnist for Rotoworld from 2009-2010. He recently contributed an article on Mike Stanton's slugging to The Hardball Times Annual 2012. Contact David at and check out his work at Journalist For Hire.

4 Responses to “Jered Weaver’s K Rate”

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  1. Baseballfan says:

    Pitching projections are tricky and not really reliable, especially when it comes to breakout seasons. I don’t know why they’re even being used in this instance. ZiPS ROS pitching projections aren’t nearly as useful as projections for offense (even then, they have it’s limitations). Nor are they of much use when a player unexpectedly has a true breakout season.

    Take Ricky Romero. ZiPS projects a 7.6 K/9 the rest of the way with a 4.12 FIP (4.67 ERA). We know Romero is better than that, and odds are, he’ll do a lot better than that.

    Or Kevin Jepsen. He has a career FIP of 2.74, a career GB% of 57%, and a 8.7 K/9 for his career. ZiPS projects a 4.53 FIP (5.14 ERA) the rest of the way. Also, with a 7.5 K/9. We know Jepsen has been incredibly unlucky. ZiPS doesn’t. We know he is a lot better than that. ZiPS doesn’t.

    Etc. etc.

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  2. cowdisciple says:

    We don’t know much about Jepsen at all — he has a grand total of 82 career innings. ZiPS certainly does hate his walk rate (his MLB career BB/9 is 3.62 and ZiPS (R) projects 5.57.)

    A 4.12 FIP in 2009 would have put Romero with Scott Baker, Weaver, James Shields, Matt Garza, etc. We KNOW he’s better than those guys, based on 80 innings in 2010?

    I agree that pitching projections aren’t all that reliable, but they’re still better than nothing and better than gut feel. They’re just a starting place, anyway — feel free to modify them.

    Thanks for the great post on a question I just emailed last night, David. I love this website.

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    • Baseballfan says:

      Sorry for not clarifying what I meant. My point is that you have to be careful with how you use them (and look at them). They’re not meant to be used to determine whether a breakout season is for real or not. Or whether a pitcher will continue to perform a certain way throughout the season. They should never be used (or viewed) like that. They have it’s limitations, and they’re not even reliable to begin with. And you’re right, they’re better than nothing, and I am not at all saying they’re useless — they’re not, you just have to be careful with how you use them and look at them. That’s all I meant.

      And you’re right, we don’t know all that much about Jepsen. However, for his career…he is throwing a solid amount of strikes for a strikeout pitcher, and he has the skillset (groundballs, strikeouts) to be an elite reliever. He certainly has pitched like one.

      Romero has the skillset to be an elite starter. Also, groundball rates stabilize pretty quickly. He has a 57% GB rate this season…and 55% for his career through 250+ innings. He also throws strikes and misses a lot of bats (11% this season). He certainly has pitched like an elite starter, and using ZiPS ROS numbers in an attempt to discredit Romero would be an insult to the pitcher and the projection system itself — it’s not meant to be used like that.

      Cheers :)

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  3. Eno Sarris says:

    This is a fine piece of writing, Goleblahblah. I think we’re seeing his peak and when he loses that 1-2 MPH in a couple years he’ll looks like he did the last couple of years. I wonder how long this peak will last. Golf clap.

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