Making a case for the DF?

Continuing my series of columns devoted to making baseball stats more meaningful and useful to fans, I turn my attention to defense, the forgotten Chinese food of the statistical fridge. Or something like that.

It seems to me that in this day in age, defense can be accounted for pretty easily with two stats. First you have Zone Rating (ZR), which is a play-by-play stat that requires stat-heads in some bunker/dungeon to log every ball put in play in every game. I’m glad I don’t have to do it, but it’s nice that someone does. So, how ZR works is simple: the field is divided into “zones,” one for each defensive position, and the ZR is simply the percentage of balls hit into the zone that a player gets to. Thus 1-ZR is the percentage of balls a player didn’t get to in his zone, and from that you can figure out how many extra hits a player allowed defensively by not getting to balls.

Now to me, I don’t see any real difference between extra hits and errors, which are addressed by the second key defensive stat, the Fielding Percentage (FP). The FP is the percentage of balls that a player gets to that are successfully played, i.e. not errors. Again, 1-FP is the percentage of balls that are played into errors, and from that you can calculate the number of “extra hits” allowed by a player when he gets to balls.

With this foundation I’ve designed a way of making these numbers a little more accessible, for each position. Understand that what follows isn’t the be all end all of accuracy. My methods use a series of approximations that the pros would scoff at, but my aim is to get more out of the numbers in a reasonable way. So with that in mind: I was able to come up with projections for how many balls will be hit each position (Zone Chances = ZC) over a season, and also the “maximum” ZR for each position since some positions are more difficult than others (+ZR), from historical data:

Now a formula can be worked out to project “extra hits” (-dHits) that a player allowed over a season compared to the best possible defender at that position:

(ZC * ZR*(1-FP)) + (ZC * (+ZR-ZR)) = -dHits

I went one more step with this. It seems fair to me that to gauge a player’s total value, you could take away the extra hits that a player gives up in the field from the hits they put up at the plate. From historical distributions it looks like the average hit is worth 1.2 bases. Over a normal 550 AB season, an extra hit that gets you 1.2 bases would be worth just about .004 points of OPS. So it could said that every –dHit is worth .004 –dOPS, and that OPS-dOPS could give you a total ratedOPS.

I’ve calculated the ratedOPS for top five qualified OPS producers at each position (other that P or C) for the 2005 season, with some pretty interesting results. The table below shows Zone Rating, Fielding Percentage, extra hits allowed, OPS given up, OPS, and ratedOPS. I’ve also included the two top ZR players at their positions whose ratedOPS is higher than some of the top 5 OPS producers.

It’s pretty amazing the effect that defense has when looked at in this way. Some players like Giles and Young are giving back over .300 on their OPS. It makes it pretty clear why you position bad defenders at the corner positions. Giambi at 1st, as bad as he is, costs the Yanks fewer hits than A-Rod at 3rd. Or take Derek Lee (.871, .996) and Andruw Jones (.873, .995), and see that Lee gave up 16 fewer –dHits. Also notice that the only two positions where a fielding ace made it into the top 5 of ratedOPS were the middle infield. I have yet to figure out the best ratedOPS players from last year, but I’ll post it when I do.

Obviously the OPS put up by DHs wouldn't be affected, and it makes you wonder, is a DF in baseball's future? Michael Young and his .545 ratedOPS could certainly use one, or at least a move to left field.

The stats that I used are publicly available on ESPN.com, and the formula I use is very simple, though it could certainly be improved. Since it’s so clear how important defense can be, I think it would be great if we could get something like –dOPS talked about and displayed in tv broadcasts, along with all the rest of the stats they show. It would really make it a lot easier to interpret the impact of player’s defensive ability.