Gil Meche famously retired and voluntarily gave up the last (I believe) $11 million of his contract because he was absolutely sick of trying to rehab his injuries, and the CBA said that an injured player had to be working toward returning to the field in good faith. And Meche was willing to sacrifice $11 million in order to avoid that misery.
I suspect that if a player flat-out refused to undergo any medical treatment for an injury and did not seem to be seriously rehabbing, then a team could file a grievance and seek some kind of financial remedy. It's difficult to imagine something that flagrant actually happening. I could see a scenario where a player opts for a treatment that the team considers unsafe, experimental or wholly inadequate, and there's a fight over that. But Strider's situation doesn't come within a hundred miles of that scenario