I agree, unless he improves dramatically I think he will be a liability on the wing.
If he does, any coach would be wise to target his side of the zone for open looks. It's not for a lack of effort, I'm just not sure he's mobile enough in terms of lateral quickness to cover his spots.
I don't think that his lateral movement is any worse than Rick Jackson's was. However, Onuaku was manning the C position, and he clearly could not play the wing. On this team, it would seem that Rak has much better lateral movement and would be better suited to play the wing.
I also am one of those in the minority who thinks Coleman can man the wing on a competitive and successful team. He already appears more mobile than Rick Jackson and Big Rick manned the wing on one of the best teams in Syracuse history. Sure, Coleman could be at a disadvantage at times defending the wing due to quickness issues and inexperience but it helps us having the best rebounder and inside scorer being on the court.It will be interesting to watch and see what happens as the season progresses.