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September 15, 2010
Fun with Opponent Quality
Player evaluation would be a much easier feat if conditions were held constant. Park adjustments and positional adjustments, among other factors, may be diverting for a select few to derive (seriously, this is the face that Colin Wyers would make if someone took park factors away), but the necessity of implementing them makes baseball analysis a lot more difficult. On the other hand, it also makes baseball analysts a lot more employed, so I’m not complaining. What’s more, even if you never find yourself staggering under the weight of a BP paycheck, you should be grateful for the complications, since idiosyncrasies like these help make baseball a ready source of almost endless discussion. Of course, I suppose that even the deprived people who follow sports restricted to playing surfaces of identical dimensions occasionally come up with something to discuss.
One factor that’s not currently incorporated into our pitcher value statistics is the quality of opposing batters, known colloquially as OPP_QUAL_OPS in our nifty “Pitcher’s Quality of Opponents” Report, in which (as one might imagine) it plays a central role. It’s tempting to act as if each pitcher faces the same caliber of competition, putting his statistics on an equal footing with those of his peers (after accounting for his home park), but the numbers belie the validity of that assumption. Among American League pitchers with a minimum of 100 IP, OPP_QUAL_OPS ranges from .747 to .715 (keep in mind that A.L. batters average .736), a disparity of a magnitude akin to that which separates the offensive contributions of the average A.L. left fielder and center fielder.
Of course, that’s the Junior Circuit’s most extreme example, but it still serves as a reminder of the difference that a pitcher’s luck of the draw can make. Naturally, relievers are subject to even more dramatic fluctuations in opponent strength; I won’t cover relievers at length in this post, but if we lower our cutoff to 40 innings, a greater gulf separates the leaders and trailers, extending from Randy Choate’s .763 to Bobby Jenks’ .700.
Here are the highest OPP_QUAL_OPS figures among A.L. starters with at least 100 innings under their belts this season. N.L. Starters will be presented separately, since the privilege of facing opposing pitchers at the plate means that they have an easier time of it overall (to say nothing of league quality):
Any Rays or Red Sox fans sweating the seemingly unsustainable performances of David Price and Clay Buchholz, respectively, might be somewhat heartened to know that their young aces haven’t been feasting on the dregs of the league. Conversely, anyone bummed about Brandon Morrow’s underperformance of his 3.15 SIERA can at least take solace in the fact that his 4.49 ERA was recorded against the toughest competition.
Any Felix Hernandez or Francisco Liriano boosters in search of additional ammunition against CC Sabathia’s Cy Young Award candidacy can fill their chambers from this table; among A.L. starters who’ve seen significant time, Sabathia has faced the weakest opponents. “But Ben,” you might ask (granted, you might not ask, but play along, for my sake), “How is it that CC’s faced the weakest competition? Doesn’t he play in baseball’s toughest division?” Well, yes. The A.L. East has put up a collective .758 OPS, compared to the measly .701 OPS recorded by King Felix’s A.L. West (two Orioles made it into the first table, reminding us how much it must suck to be Baltimore).
However, remember that Sabathia hasn’t had to face the Yankees, and Hernandez hasn’t had to face the Mariners. If we remove those two teams from the equation, the divisions grow much closer: the East and West now come in at .751 and .722, respectively. Of course, that’s not to say that Sabathia hasn’t led a charmed life (for what it’s worth, the Yankees enjoyed an easy interleague schedule this season, which might help explain how Sabathia, Phil Hughes, and Javier Vazquez own 3 of the 13 lowest OPP_QUAL_OPS marks).
Switching over to the Senior Circuit:
Haren’s high OPP_QUAL_OPS doesn’t make his trade look any better from Arizona’s perspective, but perhaps Ian Kennedy’s appearance on this list slightly eases the pain of Max Scherzer’s departure. And now for the N.L. pitchers who’ve had it relatively easy:
Over the samples of performance associated with starting pitchers, disparities in opponent quality generally aren’t significant enough to turn good seasons into bad ones (or vice versa), but they’re worth at least a periodic look. Next time around, I’ll check into which batters have benefited and suffered most and least from the composition of their opposing pitcher pools.