No – players develop with age. If you enter the majors at age 20 and your wOBA is .330, and 3 years later your wOBA is .380 – that’s not unexpected. How many players at that age experience that kind of swing in fielding ability due to random variation? Off the top of my head, the other obvious example is Yuniesky Betancourt – but that was certainly not just random variation (his hitting fell off at a precipitous rate too).

Wouldn’t it have been relatively simple to take the difference between Ethier’s first two and last two years, compare that to the average difference in UZR/150 for right fielders of a similar age and playing time (assuming the sample size is large enough), and run a t test or something? I’d venture to say this data point is pretty significant.

I also don’t like the use of the word or the concept of “outlier” when discussing samples of player performance. Everything counts.

And, like WY above, I don’t like the wording, “cost the Dodgers 35.6 runs…”

The arm ratings are always “as compared to an average player at that position.” So, when a player moves from LF to RF, we expect his arm rating to do down by X runs since the average RF’er has a much stronger arm than the average LF. I forgot how much X runs are, but it is probably 3-4 runs or so. It is like moving from 2B to SS. You expect a player’s range runs to go down by a few runs..

Is this really the best way to word this? Is it really fair to penalize him for the positional adjustment in terms of “costing” the Dodgers all these runs? After all, someone has to play right field. If his UZR were 0.0, would it really make sense to say that he “cost the Dodgers -13.9 runs with his glove”? Something’s not right there.

I think he’s just not moving as well as when he was slimmer. His power has increased though, so maybe it’s muscle weight as well.