Which Tigers starter should be in the bullpen?
posted in Sabermetrics |An intellectual exercise: Which Tigers starters are best served by being in the bullpen?
Detroit has too many starting pitchers. Like, way too many. Next year the task will be to choose five among these candidaties: righties, Jordan Tata, Zach Miner, Nate Robertson, Jeremy Bonderman and Justin Verlander; lefties Wil Ledezma, Kenny Rogers, Mike Maroth, Andrew Miller, Nate Robertson. You could throw Joel Zumaya into that mix if you like, but I believe he will make his home as a late-innings rock star, so I won’t.
What do you do with the others? You could keep them around in long relief roles. You could send them to Toledo as insurance. Or you could trade them and try to get a bat.
The reason I’m even bothering with this right now is Baseball Prospectus’ Nate Silver ran an article recently looking at finding which starting pitchers would best be served by becoming relief pitchers. Previously, his analysis found that nearly all starters, no matter who they are, will see their ERA decrease by 25% when they move to the bullpen. But some starters who made the move historically were more successful than others.
I will simplify the task by naming Tigers who I believe would never be considered for the bullpen: Justin Verlander, Jeremy Bonderman, Andrew Miller and Kenny Rogers. (As of right now, I would have those four in my rotation next year, but the Tigers may disagree. In any case, they’re not changing roles). Guys who I believe are fighting for the fifth spot: Mike Maroth, Nate Robertson, Wil Ledezma. Guys who I believe probably aren’t: Zach Miner, Jordan Tata. I’ll look at those five and see if there’s any optimization we can do, as to starter, bullpen, trade or keep as insurance.Silver’s research found the following correlation to relief success:
BB Rate +.210
K Rate +.201
BABIP +.002
GB% -.002
Age -.142
ISO -.274
That is, one the best predictors is a high strikeout rate. He points these are above the expected success of these stats. Counter-intuitively, a high walk rate is also a predictor of success. Why? Silver says over six innings, pitchers who struggle with mechanics will thave their wildness will catch up to a starter. Over one or possibly two innings, it probably won’t. Finally, the best predictor is a guy who doesn’t give up a lot of extra-base his. That makes sense. Statistically speaking, everything else you know about a pitcher dissolves. Flyball/groundball tendencies, average against, age, heart-attacks given to fans, none of it matters.
A relief role emphasizes high-impact pitching and deemphasizes consistency and durability. A low ISO is a good proxy for high-impact pitching, a pitcher who can take control of the at-bat with one or two great pitches. … All of this seems intuitive enough. Nevertheless, it’s routine to see teams employing pitchers in starting roles even after they’ve demonstrated time and time again that they lack the mechanical foothold to throw six or seven innings without giving something up.
No Tigers pitchers make his top five “who should switch” list. But using those key stats: K9, ISO and BB9, we see:
| Name | K9 | BB9 | ISO |
| Nate Robertson | 5.90 | 2.90 | .165 |
| Wil Ledezma | 6.26 | 3.67 | .084 |
| Mike Maroth | 4.12 | 2.81 | .187 |
| Zach Miner | 5.89 | 3.06 | .143 |
| Jordan Tata (AAA #s) | 6.34 | 3.61 | .116 |
Another few thoughts: Don’t dump Fernando Rodney after this year unless he wants a lot of money. If he does, don’t even sweat it. Worried about Humberto Sanchez’s elbow and want to keep his innings down? His numbers this year make him an excellent bullpen candidate too based on that criteria. His ISO is way low (.086), his Ks are way high. Obviously we’d rather see him starting in 2008 if he’s healthy, but it’s a thought.
What do I find? Detroit’s starting rotation looks very good up and down the club. The bullpen looks really fine, too. This team has a real future ahead barring unforseen circumstances and has a lot of flexibility. It is good to be a Tiger.
Different conclusions? Thoughts on Silver’s criteria? Let me know in the comments. If you guys like when I try applying Baseball Prospectus studies to Detroit, I’ll try to do more in the future and offseason.
Sphere It
How in the world does ESPN justify ranking the Tigers sixth?????? They have struggled, I understand, but that’s just absolutely ridiculous. The Angels ahead of them?!?!?!
Robertson’s a lefty - but you probably knew that…
[...] Wil Ledezma is charged with making today a Happy Birthday. He’s been outstanding since his move to the rotation. Leyland didn’t let him throw more than 71 pitches in either start, in part due to a stretching out phase, and in part because he was going on 3 days rest. (Speaking of Ledezma, Kurt did some interesting work extending research done by Nate Silver and found that under Silver’s methodology Ledezma may be the current rotation candidate that would most benefit from a move to the pen) [...]
Paul,
Do you really think the Tigers are the 6th best team in baseball at this point? That to me seems overly generous. I can guarantee you every possible playoff opponent is praying they draw the Tigers if they make there way in.
duh, me, thanks for the correction.
I do think they are at least the 6th best. Slides happen and the timing is absolutely awful, but they are still a top team with that pitching. Their hitting is in a team-wide funk. I’m not the always-optimistic kind of homer either, so this is what I truly believe.
Honestly guys I don’t know where I’d put em. Behind New York. Both of em. Behind Oakland. But ahead of LAA. Debatable if you want to put them behind or ahead of Minnesota. They did just win (thurs.) in the Metrodome and they’re only one game worse in the past 10. I’ll go with this top five.
Yanks
Mets
A’s
Tigers
Twins
Kurt, this is great stuff. I for one love to read deep analytical stuff about the Tigers. I usually do a lot more of that myself during the off-season when there are no games to talk about.
I tend to agree with your thinking about the Tigers starting rotation for next year although I think there is a decent chance they may trade someone like Robertson for a hitter. There is not much available in the free agent market next year so a trade might be the only way to get a much needed offensive upgrade.
Thanks, Lee. That was fun to do. Maybe I can find some more topics of research to apply to Detroit, and I look forward to your offseason writings.
PLEASE, PLEASE, PLEASE…..lets not forget about Kyle Sleeth! Still on the 40 man roster he is! This guy should be ready to blossom! I believe the Tigers are counting on it!
[...] –Finally Morosi has a bit on Jamie Walker, LOOGY, who could cost $3-4M. Bilfer asks if he’s worth it at DTW. My answer is no. Not at that cost. Not when you consider the natural home for Wil Ledezma is relief and he’s a left hander. While having an occasional excellent start, I believe he’s perfect in the pen and can replace Walker fine at no additional cost. [...]