Q&A: Glen Perkins, A Twin, His FIP, and Math

Glen Perkins knows his FIP. He also knows his HR/9, Z-Swing% and O-Swing%. More importantly, he understands what they mean. As the Minnesota Twins left-hander says, “I like baseball and I like math.”

Perkins is more than a stat geek. The 30-year-old converted starter is one of the better closers in the American League (despite his skepticism of modern-day closer usage). Six weeks into the current campaign he’s well on his way to topping last year’s save total, despite a markedly higher ERA — a number he considers less important than his FIP.

Perkins talked about his 2013 numbers prior to last night’s game at Fenway Park.

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Perkins on knowing the numbers: “In 2010, when I was in Triple-A, I came across a FanGraphs story about Brandon McCarthy and how he was changing his pitching style to get more ground balls and maximize his abilities. From there I started reading more and more. I’ve always been a math guy and the two sort of go hand-in-hand. I like baseball and I like math.

“In 2008, I thought I’d had a good year. I won 12 games and had a 4.40 ERA. That wasn’t great, but I was like, ‘that’s not bad.’ But the more I read, the more I came to realize it’s not about wins. It’s about the quality of the innings you pitch, and my quality wasn’t that good.

“In 2009, I started out the season with three eight-inning starts and only gave up three runs total. But I only struck out 10 guys in the 24 innings. I read somewhere that I was going to regress. I thought ‘What?’ It didn’t make sense to me. That’s when I began poking into it, but I mostly brushed it aside. Then, in 2010, I started reading more and more. I began to realize wins were a result of quality innings, not the barometer of how good you are.”

On what he considers the most important pitching stat: “Fielding Independent Pitching [FIP]. That’s what a pitcher can control, and the lower it is — just by default — the lower your ERA is going to be over the course of time. Not walking guys, getting strikeouts and ground balls, and not giving up home runs, are the keys. I don’t ever want to walk a guy and would strike everyone out if I could. If I can’t strike them out, I’d like to jam them so they hit a pop up to the infield, or a ground ball.”

On if his 13.5 K/9 is sustainable:
 “The last two years it went up. My swinging-strike rate has gone up. I know my chase-rate is down, but my in-zone swing-and-misses are higher this year than last year. Obviously it’s a small sample.

“So, I don’t know. I’d like to think so. I don’t know if there’s a stat for an expected strikeout rate based on swings-and-misses and chases. I guess maybe where I’m at is a little high, but I think I can improve from last year when I was at 10 per nine.”

On his O-Swing% [38.9] and Z-Swing% [71.4]: “I typically know what gets swung at — it’s usually fastballs up and out of the zone, and sliders below the zone. Having a higher O-Swing rate obviously means they’re chasing pitches, but it also means they don’t know what’s coming — or they can’t react. That’s a good indicator of how much chance a hitter has. Getting big-league hitters to swing at pitches out of the zone is hard to do. Getting big-league hitters to swing and miss at pitches in the strike is even harder. But you can make quality pitches in the strike zone, and I feel my stuff allows me to pitch in the strike zone.”

On his F-Strike% [74.4]: “It’s a known fact that a guy hitting 0-1 is significantly worse than a guy hitting 1-0. Getting to 0-1 is also the quickest way to 0-2. At 0-2, a hitter has a very small chance and that chance is probably a single. But you can’t just throw it down the middle of the plate. For me, getting to 0-1 is just as likely to be a competitive slider down in the zone, or even below the zone.

“In most of the situations I’ve pitched in this year, we’ve been leading. Guys are typically taking a pitch in that situation — I’ve known they might be giving me that first pitch — but even so, you never throw a ball down the middle. I might throw a four-seamer in or I might throw a slider.”

On his BB/9 [3.38]: “I think my walk rate right now is mostly based on small sample size. I did this last year. I had a game against the A’s where I walked three guys in one inning, and outside of that I only walked 12 or 13 guys all year. This year, two of my five walks came in one game against the Rangers. Good command is the last thing to come. As the season goes on, I get more comfortable with my delivery.”

On his GB% [26.1]: “There’s a small sample size there as well, but so far this year I’ve struggled with extension. As a result, I haven’t had as much downward action on my ball. But I pitch more with four-seamers now, and… I don’t know what the swing rate is on my slider, but I would imagine that’s my main ground-ball pitch. I haven’t gotten a whole lot of balls in play on my slider.

“The two-seamers haven’t been there. I didn’t throw a lot of them last year. From 2011 to 2012, the usage of those two kind of flip-flopped. My four-seamer comes in harder, so I’m throwing more of those.”

On his HR/9 [0.84] and HR/FB [10.0]:
“In 2011, I only gave up two home runs. I got a ton of ground balls — it was just under 50 percent — and last year my fly-ball percentage and home-run percentages went up. I think I was right around league average on home-runs-per-fly ball. I would assume that this year, at whatever point that stabilizes, I’ll be around 10 or 11 percent. That’s why I’d like to get more ground balls.

Greg Maddux said to me at the World Baseball Classic this year, ‘If you get your balls hit in front of the outfielders, you did your job.’ Some balls are going to fall in and there are going to be line drives hit right at guys. It’s about not letting the ball go over the fence.”

On his ERA [4.22] and FIP [2.34]: “My [current] ERA isn’t a concern to me. My main concern is what I’ve done in the seven games where I’ve come in and gotten a save. I’ve given up something like four hits and one run and struck out 13 or 14 guys, in those seven games.

“In one game we lost 16-5 [to the Mets] and I gave up two runs. In another game we lost 7-2 to the Rangers and I gave up two. Outside of that, I’ve given up one run. As time goes on, my ERA is going to get closer to my FIP. The more I minimize home runs, the lower my ERA is going to get.”

On being 7-for-7 in save opportunities: “Do I particularly agree with closers in baseball? That’s a tough question that I ask myself. But it’s my job, and when I go out there to do that job, saves are the most important thing to me. If I throw a quality inning, that’s the result I should get.”




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David Laurila grew up in Michigan's Upper Peninsula and now writes about baseball from his home in Cambridge, Massachusetts. He authored the Prospectus Q&A series at Baseball Prospectus from February 2006-March 2011 and is a regular contributor to several publications. His first book, Interviews from Red Sox Nation, was published by Maple Street Press in 2006. He can be followed on Twitter @DavidLaurilaQA


25 Responses to “Q&A: Glen Perkins, A Twin, His FIP, and Math”

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  1. Andy says:

    This was an awesome article. I love these player interviews.

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  2. Jon Roegele says:

    Wonderful interview. Amazing to hear a player speak so confidently and in such depth about his own advanced metrics like this. Very cool.

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  3. Dan Rozenson says:

    I think I love him.

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  4. Pr says:

    great piece. I wonder what these pitchers think about FIP vs xFIP. Does he look at his fly ball rate or actual HRs allowed

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    • leeroy says:

      saw a twitter convo he had the other day talking about his xFIP going down despite him allowing a HR which made his FIP go up.

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      • Bryz says:

        Yep, he was discussing a home run he allowed and he noted that since his HR/FB came closer to the league average after that game, his xFIP would go down even though the HR would cause his FIP to increase.

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        • Requiem says:

          That doesn’t sound quite right.

          His xFIP shouldn’t go down BECAUSE of the HR allowed. It should just not increase like FIP would.

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        • philosofool says:

          Yeah, xFIP just replaces home runs with FB and changes the coefficient to 13x where x is HR/FB. So a fly ball will increase xFIP.

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  5. Reptar says:

    Very nice article. If I didn’t know better I’d swear this was some sort of Fangraphs fan-fiction. His answers read like advanced metric porn.

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  6. Neil says:

    As a Tigers fan, I make a general rule to never like a Twin, but man, it’s hard not to here. Awesome.

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  7. CSJ says:

    A quick and dirty thing I just did: Expected K/PA equals 0.0633 + O-Swing(pfx)*-0.2315+SwStr%*2.192. The negative o-swing coefficient is strange, but o-swing is not very closely correlated with K/PA (r^2 about 0.14)

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  8. 8nthatk says:

    What a great read. My second year as a happy Fantasy Perkins owner to boot…

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  9. A Twins player reading into sabermetrics? I can’t even…

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  10. Perkins should be the Twins Player/GM.

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  11. Metsox says:

    That is an amazing piece.

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  12. tz says:

    It would be neat to be able to split batted balls between those hit in front of outfielders and those NOT hit in front of outfielders (per the Greg Maddux comment to Perkins)

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  13. Kevin says:

    very cool to hear his reasoning and explanations for his statistics. sabermetrics is getting better and better at explaining player performance, but there are still very definite limits to what we understand. insights from perkins and other stats oriented players and baseball personnel help fill in those gaps. a great read.

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  14. adohaj says:

    Go twins! Metrics and projections be damned, I have hope for this year!

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  15. Ron Gardenhire says:

    “I… would strike everyone out if I could.”

    Anybody with Perkins on their fantasy team should probably trade him now.

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  16. eddiegaedel says:

    Seems like a “Quality Inning” stat could be really fun in fantasy baseball, rather than Innings Pitched, Quality Starts, or Wins. Not sure how to quantify that but I like the way Glen looks at it. This series is awesome but this has been the best one yet.

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  17. Ben Hall says:

    Bill James used to (maybe he still does) use the term “relief ace” when he was looking at optimal reliever usage. Perkins seems like a great guy for a progressive team to have, because the main argument I’ve seen for teams continuing to use closers, set-up men, etc. in very defined roles is that the pitchers feel more comfortable in those roles. It seems clear that Perkins would feel perfectly comfortable being used at any time, understanding that a manager was using him in the 7th inning with the bases loaded because that was likely to be the most important situation in the game.

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  18. MN_Oldgoat says:

    Awesome article. Thank you David. Thank you Glen.

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  19. jkud says:

    Where can we find more of the Q&A’s? Pretty awesome.

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