The two knocks on his game going in to the draft were that he's not a great scorer and he's just an average skater. Sure, he's winning faceoffs and that's great but without the goals and without him being great on his skates, it doesn't make much sense to have him manning the middle.
Him being an average (or even below average) goal scorer wouldn't affect his ability to be a center though. Historically, centers are play makers who are generally pass-first anyway. Look at a guy like Mike Ribeiro and he's not a goal scorer at all. In terms of skating, its not uncommon for centers to not be as fast as wingers. A lot of center prospects get knocked for their skating around the draft too but skating is probably the easiest thing to improve on. Based on what we've seen though this yr as a pro, his skating doesn't seem to be a liability at all.