If it is win or be fired the man has a need to select assistant coaches as he sees best. And it is win or be fired.
Sherels has had medical problems, and Coyle should consider, if NCAA allows it, an athletic department position as program-wide recruiting overseer. Without any coaching contact, but attentive to each program's recruiting needs and balancing budget that way, between programs. Dealing with the head coaches, perhaps, if NCAA permits, talking with recruits before they commit to a school.
Clearly the medical condition is unfortunate, but it appears Sherels can remain helpful to the Department. However, NCAA rules have to be honored to avoid sanctions, so the situation is pending.
Strib reporting, here. There is no cause to blame or criticize Fleck's decision making about Sherels. Having to produce a winning program he must have discretion to pick his assistants freely as he believes best; whatever his reasoning. It is how the job works. It was how Claeys moved in changing offensive coordinators, in his best judgment.