Admittedly, he is subpar, relative to the avg small forward, in rebounding (by about one board per 48 minutes), and assists (by half an assist). He also averages about half a steal less per 48, but that's offset almost exactly by his lower turnover rate.
Weighing against those seemingly modest deficits, his shooting efficiency is at an elite level this season -- and I don't think I'm using "elite" lightly. His true-shooting percentage is 61 -- 7 full percentage points better than that of the avg small forward. He's averaging 1.4 points per shot. And while he's not a huge usage guy, he's scoring (per 48) just two points less than the average SF.
Don't get me wrong: I don't think Martell is an all-star or anything. And he's been helped out a lot by the team around him this year. But I think he's definitely been better than the average starting SF this year. (Whether he's having a career year is a different question -- I think he probably is.)
Wages of Wins, for comparison, rates him very highly: they attribute more wins to him than any other Wiz player so far this season (taking the whole season into account), and put his wins-per-48 at 0.17, which is very high.
So what does everyone think? Am I overrating Martell? Or is this an example of the (significant) limitations of PER?