Go back and watch Corbin's game 4 against the Cardinals. As long as batters swing at the slider spinning into the dirt, he is over-powering. His 94-95 mph fastball has to be accurate enough to make the slider work. When batters stop swinging at the diving slider or he starts missing with the fastball, he collapses. Maybe that's mental -- he certainly never recovers.
The Nats are stuck with Corbin for a couple more years.
Davey has to let Corbin start and pull Corbin just when he slips. Right now, that has been after five or six innings. That's probably good enough to win half Corbin's starts, although it's tough on the bullpen. Good to have relievers like Klobo, who can go two innings.