It looks to me like a mental issue since he does not appear to have an injury. Coach Self appears to still have faith in him and he is getting playing time.
Coasting at this time would have dire consequences, unless he is planning on coming back, which is always a possibility. In the last few weeks he has played himself out of the first round and continued below average play will push him out of the draft altogether, not something any player would want even if planning on coming back.
KU needs him playing at a high level for the team to do well; obviously he is not the most important player on the team but a very key part of it; his level of play in the upcoming weeks might determine how well the team does and how far it advances.