It's not just a great track from the best rap group ever, it's also a solid handicapping lesson. As I was doing the homework for tonight's games, I noticed something I found interesting about a couple of tonight's starting pitchers. When trying to anticipate a pitcher's performance in a game, there are some statistics that can be heavily dependent on factors other than the ability of the pitcher. For example, a pitcher's win-loss record is pretty much a useless way to measure a pitcher's ability. Whether a pitcher gets a win or loss in a game often depends less on the pitcher's performance in that game and more on the run support, fielding, and bullpen effort in that game. A pitcher's ERA can also vary depending on the quality of the defense behind him, among other factors. Outfielders who have speed and strong throwing arms, and/or shortstops who can make difficult catches and tough throws either to first to get the hitter out or to second to start the double play, can keep a significant number of runs off the board, thereby reducing a pitcher's ERA.
On the other hand, as my blog partner, Grover, has pointed out before (and provided links to articles by smart folks who are much better at math than we are), there are several statistics which are solely based on a pitcher's performance, and are not dependent on his team's defensive ability at all. Such defense-independent statistics include home runs allowed, strikeouts, walks, and hit batters. The number of hit batters is usually not high enough to be a big factor by itself, but since the hit batter results from a similar lack of control and produces the same result as a walk (batter gets a free pass to first base), I'm going to add walks and hit batters together for purposes of this post.
Now, borrowing a gimmick popular with fantasy baseball writers, compare the 2008 defense-independent statistics of these two pitchers (both starting Friday night):
Pitcher A: 5 home runs allowed, 22 strikeouts, 27 walks & hit batters
Pitcher B: 6 home runs allowed, 22 strikeouts, 25 walks & hit batters
That's pretty damn close. So, obviously, these two pitchers are having similar levels of success this season, right?
Wrong.
Pitcher A is Gavin Floyd, who has a record of 4-2 and an ERA of only 2.92.
Pitcher B is Barry Zito, who has a record of 0-8 and an ERA of 6.25.
The point? Most importantly, the win-loss record is garbage when evaluating the performance of pitchers. Although the defensive fielding numbers (fielding percentage, errors committed) are virtually identical, Floyd has the advantage of an offense that has scored a lot more runs than Zito's team, and the White Sox bullpen has performed much better than the Giants this season. That doesn't make Floyd a better pitcher than baseball's poster boy for ridiculous contracts; it just makes him lucky. Similarly, the difference in ERA between the two starts to make sense when you compare their BABIP numbers Just because the batting average on balls in play for the hitters Floyd has faced so far (a ludicrous .193) has been unsustainably low when compared to Zito (.359), doesn't mean Floyd has pitched better. It just means he's been lucky so far. And luck doesn't last. Don't accept the stats displayed on ESPN's scoreboard at face value. Scratch beneath the surface to find out if a pitcher really deserves the praise (Floyd) or scorn (Zito) that he's getting from the folks at SportsCenter before you put any money into play.
Note: The points I make in this post only apply to predicting a pitcher's likely performance going forward or in a particular upcoming game. Of course, the pitching performance is not the only factor involved in deciding whether to bet on (or against) a particular team. All the factors discussed above, which can artificially skew a pitcher's statistics, are still extremely important when handicapping a game and all have an important effect on whether a team wins or loses. But, when you're focusing on the pitching part of your analysis, make sure you're not overvaluing or undervaluing a particular pitcher based on factors he can't control.
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