Too bad more managers don't own race horses. If they did, they would know about peaks and valleys of an athletes performance. When a horse declines in performance, he is telling everybody it's time for a rest. So the trainer turns him out for a few weeks. The horse comes back and wins a few races--then trails off--time for another rest. It's called conditioning.
Ballplayers are like race horses. When they slump, it means they are tired--physically, mentally. Turn 'em out a few games. Freshen 'em up. Unlike horses, ballplayers can talk. But they aren't going to tell the manager--hey I need a rest. The manager has to know.