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Sunday, February 17, 2008
How many runs is a good fielding SS worth?
From 1957-2006 (excluding 1999), there have been 50 shortstops that have played at least 1037 games at SS (specifically, at least 28,000 outs). This is what I did. In 1977 at Olympic Stadium, ten of these 50 shortstops played there. In all, their teams allowed 4.15 runs per 9 innings, on a total of 1156 innings. In the 336 innings that these ten shortstops did not play at Olympic Stadium in 1977, those teams allowed 4.23 runs per game. It is a reasonable expectation that guys who played the most SS in MLB since 1957 are at least above average fielding SS. And, this little data here points in the right direction: our good fielding SS, when they were on the field, allowed .08 fewer runs per game than the rest of the league.
I repeat this for all parks in 1977. I repeat this for all years. What we end up is the performance of teams with good fielding SS, compared to their counterparts in the same parks in the same years. What are our totals?
Our 50 shortstops with the most playing time played a total of 682,330 innings (468 full seasons). Their teams allowed 4.30 runs per game. Their counterparts (all other SS, weighted by the same park/year combination) allowed 4.54 runs per game. Therefore, our top 50 SS were on teams that allowed 0.24 fewer runs per game than their counterparts. That’s a nearly 40 run difference over a full season, which is quite hefty.
Surely, there must be some other bias? I’m guessing that these 50 SS played on better than average fielding teams, and those teams may have had better than average pitching. We neutralized for the park, so that’s not an issue. Still, it’s hard to believe that there could be that much of a bias over those many innings.
I tried to look at a subset of those 50 fielders. I have my WOWY system that evaluates who are the best fielding SS. I looked at the top 20 of those. I then asked Rally for his list using his own system. I looked only at his top 10 SS. Nine of those were in my top 20. So, I considered those 9 SS to be the best fielding SS since 1957: Aparicio, Belanger, Brinkman, Campy, Greg Gagne, Guillen, Ron Hansen, Bill Russell, and Ozzie.
I repeated my process, but this time, rather than looking at the 50 SS who played the most in MLB, I only looked at these 9. the cream of the crop. And in 143,520 innings (98 full seasons), the teams when these guys were on the field allowed 3.98 runs per 9 innings, while their counterparts allowed 4.28 runs, for a difference of 0.30 runs per game.
I agree with you that this is fairly high. My WOWY system puts the nifty 9 at being 0.15 runs per game better than average. The implication here is that there is a sufficient bias to account for an extra 0.15 runs per game on top of that (to get us to +0.30). Belanger had Brooks and Grich and Paul Blair. Ozzie had Pendleton. It’s possible that there is a bias in that good fielders attracts other good fielders and good pitchers.
Even so, I was surprised by the rather large difference.