I think he can. Bagley pulled out a couple switches tonight that we didn't see last year. He got some bs called against him but if he picks up how to not let his man get behind him on lobs he's got the tools. Holmes clearly has been taught very well when it comes to defensive IQ.
He flashed decent man defense at times last season, and blocked more shots per game than he did in college. The desire is there, he just needs a good teacher.