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September 20, 2012

Overthinking It

No Ace, No Problem?

by Ben Lindbergh

As October approaches, several contending teams find themselves without ironclad aces at the top of their rotations. The Rangers will go into Game One with Yu Darvish, who’s riding a string of several strong starts but has struggled at times during his debut season. The A’s may have to enter October with an all-rookie rotation lacking both Brandon McCarthy and Brett Anderson. The Orioles’ rotation is fronted by Wei-Yin Chen, who’s been barely better than league average. The Cardinals are hoping the reckoning for Kyle Lohse doesn't come until 2013. Should the Dodgers claim a wild card, their hopes of advancing to the NLDS might depend on Josh Beckett. And even Yankees ace CC Sabathia has looked uncharacteristically shaky in the second half.

Meanwhile, a few other playoff locks and hopefuls can count on handing the ball to a starter who’s been consistently successful all season. The White Sox (Chris Sale and Jake Peavy), the Nationals (Gio Gonzalez and Jordan Zimmermann), the Tigers (Justin Verlander), the Reds (Johnny Cueto), and even teams on the periphery of the race like the Angels (Jered Weaver) and Rays (David Price) can rest secure in the knowledge that their top starter would match up well with any opponent in a play-in game or at the start of a series.

Aces are often viewed as integral to post-season success, but do the teams with stronger starters at the tops of their rotations really have more reason to be confident?

We can all recall teams whose playoff success (or lack thereof) supported either the Essential Ace Theory or the Extraneous Ace Theory. The Braves won the World Series only once during their streak of 14 consecutive playoff appearances, despite having three Hall of Fame-caliber starters in their rotation for the majority of their run. The Phillies won the World Series in 2008 with a rotation topped by Cole Hamels and Jamie Moyer, then got bounced in the first round three years later despite replacing Moyer with Roy Halladay, Cliff Lee, and Roy Oswalt. The 2005 White Sox won on the strength of four dependable-but-not dominant starters, all of whom made at least 32 starts but none of whom struck out as many as seven batters per nine innings. The 2002 Angels went all the way with Jarrod Washburn, who never made an All-Star team.

Obviously, having an ace is no guarantee of October success, and lacking one isn’t a post-season death sentence. But anecdotal arguments won’t get us anywhere. To come up with an answer, we have to examine how all playoff teams have fared.

To do that, BP Director of Research Colin Wyers selected the “ace” of each playoff team from the one-wild-card era of 1994-2011, defining the ace as the starter who pitched at least 120 innings with the lowest ERA. Then he came up with a normalized measure of “ace-ness,” similar to ERA+ (2-ERA/lgERA, to be precise), that allowed us to place all the aces on the same scale. Finally, he checked the correlation between the strength of each team’s ace and the difference between its winning percentages in the regular season and the postseason.