It's Not Whether You Win or Lose, It's Whom You Play
An oft-overlooked piece of information by baseball analysts is strength of schedule at the player and team level. As the regular season winds down and we try to determine who has been the best team in baseball , as well as the Most Valuable Players and Cy Youngs of both leagues, I took a look at quality of opponent to see who has been helped and who has been hurt by the competition.
Giving credit where credit is due, to my knowledge Baseball Prospectus continues to hold the best readily available data on quality of opposition. On BP's adjusted standings page, there is a column for expected runs based on a team's batting line (UEQR) and another column for that same stat, except adjusted for strength of schedule (AEQR).
I plotted the difference between how many runs a team should have scored/allowed with the same number adjusted by strength of schedule. The scale is not very intuitive, so I will explain that teams in the upper-right quadrant have scored more runs and allowed fewer runs due to a relatively easy strength of schedule, while the reverse holds true for teams in the lower-left quadrant.
If you look closely, you may noticed that each quadrant is made up of mainly teams from the same division. You see that the AL East may have the highest quality of play, the AL West the best run prevention or worst run scoring, the NL East the best run scoring or worst run prevention, and the NL Central the lowest quality of play.
Given a fair strength of schedule, the Orioles would have been expected to score some 20 runs greater and allow some 20 fewer with a fair strength of schedule. Given this fact, as well as Baltimore's youth, and the concept of regression to the mean, you can already mark me down for the Orioles' over next year. Because of the potency of the Yankees’ lineup, the rest of the AL East actually should have earned better run production marks. Unsurprisingly, the Jays and Orioles have the largest difference between their second-order wins and third-order wins, or in English, they have faced the most skewed schedules in baseball.
Adjusting for luck and schedule, the Indians have carried the strongest offense in their division by a fair margin, and will surely make for a trendy pick, as usual, among analysts in next year's predictions. With my apologies to Rich Lederer, who is probably tired of his Angels’ Pythagorean record being discussed, I have to mention oddities in the Angels’ record. Not only have they managed to outplay their run differential, but according to BP, the Angels’ have gotten lucky in the number of runs they've scored and allowed. The Halos are really the only team in their division that can hit, so their staff is likely not as good as we think. Furthermore, Angels hitters lead the league in BABIP and have been unusually successful with runners on base as compared to their production with the bases empty. However, each team in the AL West plays defense ranging from above average to excellent, so to be fair, the entire division's run-scoring has been depressed by playing each other.
The American League owned a .546 winning percentage in Interleague Play this year, marking the fifth straight year of American League utter superiority. I do wonder whether any National League team would have boasted a winning record playing in the American League East.
To check out individual players' quality of opponent, I moved on to BP's quality of batters and pitchers faced reports. The reports give quality of opposition in terms of the triple-slash-stat line.* I limited my sample to pitchers with at least 300 batters faced and batters with at least 300 plate appearances.
*Instead of GPA and OPS, why haven't we ever used what I believe to be the most sensible combination of OBP and SLG, 1.75 multiplied by OBP and then added to SLG? We could then keep it on that scale, which has a league average of exactly one, as in 1.00. Wouldn't that be a rough measure of offensive production that makes everyone happy, more or less?
The eight pitchers in baseball, and 14 of the top 15, who have faced the highest quality of opposition all hail from the American League East, including Roy Halladay coming in second to David Hernandez. Roy Halladay is awesome. Again, to illustrate the difference in quality of play between the leagues, I will refer to John Smoltz and Brad Penny. The opposing batter's quality of slugging percentages against Smoltz and Penny have gone down 20 and 11 points respectively since the pair left the AL East. Cliff Lee's difference has been a mere seven points in slugging. Todd Wellemeyer has had the easiest go of any pitcher this year.
You may not know of the stat kept at Baseball Reference called platoon percentage, but I feel it is an important piece of information in showing the competition a player has faced. Paul Maholm, whose platoon split I looked at last week, has been unlucky enough to have had the platoon advantage least often among pitchers with at least 100 innings.
The top six pitchers of the year in each league, in my opinion, excluding Lee who split time between leagues and whom I already mentioned:
Chase Headley and Kevin Kouzmanoff, who both might actually be quality Major Leaguers, have had the misfortune of not only playing half their games in Petco, but also facing the most difficult slate of pitchers among hitters. This list may well be flawed, since pitchers who get to throw multiple times against the Padres will have their stats inflated. This might be the reason that Padre hitters appear to have faced quality pitchers. Following this logic, it makes sense that Melky Cabrera and Derek Jeter have faced the pitchers with the aggregate highest opposing OBP and SLG against since these pitchers have been subjected to the Yankees. I'll present the list anyway.