Coaches/Managers who quit on their teams

Supposedly that’s what happened to the '64 Phillies. Gene Mauch was a real in-your-face guy, he wasn’t above throwing a temper tantrum to get his point across, and it eventually took its toll on the team. That and the fact that by September the Phillies were essentially down to two starting pitchers and Mauch overused them down the stretch.

Ron Washington resigned from the Texas Rangers in September 2014. From his Wiki:

Bill Bellichick left the Jets after one day on the job to go to the Patriots.