Though Nixon's natural speed is unspectacular, he makes the most of it in every way. With good reads and all-out hustle, he covers Fenway's cavernous right field very well . . . Some right fielders have a strong arm; Nixon has one but also anticipates where the throw should go in every situation. . .

Rob,

Good article about Trot Nixon! As I'm sure you know, Win Shares is not very good at evaluating defense. As I'm sure you also know, Win Shares in general is designed more to "evaluate" actual performance rather than ability, which although related are not the same thing. In other words, Win Shares is better at answering questions like "Who had the greatest contribution to their team or created the highest value to their team, rather than who was the 'best' (hitter or fielder), in terms of theoretical contribution or value to their team, which is essentially the same thing as who you would rather have on your team or who would most likely provide the greatest value to a hypothetical team or a team in the future.

Anyway, the principal reason why defensive Win Shares is not a good evaluator of defensive ability is that any defensive "metric" that does not use play by play data is necessarily not very good. I suppose it is OK to use defensive Win Shares to compare one player to another as long as one keeps in mind that the result of the comparison does not have a high degree of certainty or confidence attached to it. Sort of like comparing two players' batting averages. Although the one with the higher BA can be stated as the better of the two players if we knew nothing else about wither player, our level of certainty in that result would be low.

In any case, as you probably also know, the best metric for evaluating fielders is my Ultimate Zone Rating, at least in my very biased opinion. According to Nixon's 1999-2002 UZR "ratings" (runs above or below the average right fielder), he is indeed a great fielder. In fact, his four-year average UZR is +23 runs per 162 games, which is fantastic for a right fielder. If we had UZR ratings for all right fielders ever, that +23 over 387 games could easily rank in the top 10 or 20 of all time, and certainly in any list of the top right fielders in Red Sox history.

Of course, because it is based on "only" 387 games, his "true" UZR rating is probably somewhere around 18-20, after we regress that sample UZR. Still great, though.

Unfortunately, his arm rating, according to my data, is well below average, which belies the information in your article. Keep in mind that my "arm ratings" are very reliable and accurate (basically, they rarely lie), as they are based on the percentage of runners that advance one or two bases or get thrown out trying to advance on the percentage all of the various advancement opportunitites, etc. Nixon's "arm runs" for '99-'02 are a composite -4, which is very bad as arm ratings go. It is extremely unlikely that he has even an average arm, and it's very likely that his arm is terrible.

As far as his "progression" or decline since 2000 (according to Win Shares) . . . One most year-to-year patterns for offensive and defensive metrics are illusions (they are basically random fluctuations), so they should almost never be paid attention to, at least as far as ability goes. It is true that a player's defensive skills decline almost from the get-go for all positions other than first base, but the non-critical defensive positions (the ones not up the middle) decline less rapidly than the up-the-middle positions. In any case, Nixon's year to year UZR ratings (per 162 games) for defense and arm are:



      UZ  Arm
1999  18   -5
2000  30   +2
2001  22   -7
2002  21   -6



So, even if we paid any attention to year-to-year patterns, there is no declining pattern in Nixon's UZR or arm ratings.

Just thought I would give you some additional thoughts and data on the Nixon thing. Take care.

1. Of course!

2. Yes, my arm ratings include "park adjustments." The only park where it makes a huge difference is in Colorado, where it is extremely difficult (15 percent more diffucult) to throw runners out or prevent them from taking the extra base, presumably because the outfielders play so deep.

Fenway has an "arm park factor" of .98, which means that it is slightly more difficult to advance, presumably due to the left fielder playing much shallower than in an average stadium. In fact, the arm park factor for left field at Fenway is .90, and in RF it's 1.09. I should use separate arm PF's for each OF position, of course, but alas I only use one composite OF arm park factor for all positions, which means that the PF I use for Nixon, which is the .98, should be the 1.09. That means that I am, indeed, underrating Nixon's arm.

So let me redo his arm rating using the new RF park factor at Fenway (I am using 1.05 rather than 1.09, as I always regress my sample park factors to take into account sample error. Even thought the 10-year sample RF arm PF at Fenway is 1.09, it is likely that the true factor is closer to 1.00 and that the 1.09 is somewhat the result of random fluctuation, as there is nothing extraordinary about RF at Fenway to "justify" a true RF arm PF of 1.09) . . .

Well, I reran his arm runs, and using the new park factor doesn't make much difference. His new '99-'02 arm linear weights per 162 games are:

99 -4
00 +2
01 -5
02 -6

So again, it looks like his arm is indeed not very good.

Mickey