According to Josef Ka's analyis, this guy's skills put him at a cap number of 26.09, where MVP potential covers 26-28. So, if he has sublevels in some of those skills, and he has on the low end of MVP potential, he could certainly be capped.
One thing you could do to test that would be to train something that you know is at a high sublevel, but that won't impact his cap number overly. Passing would be a good choice I think- and he could use more passing anyway. If that's close to popping but doesn't when you train it, he's capped.