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
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, itâ€™s routine to see teams employing pitchers in starting roles even after theyâ€™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:
|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.