It's definitely a mental issue rather than a physical one and that's a good thing. It means the only thing keeping him from dominating is getting his head sorted out. If it was a leg problem he might never be able to play to his full potential again. Right now he's inconsistent and frequently overthinking but sometimes he stops thinking and suddenly looks like his old self again. Honestly I'm happy that he picked a contract year to have these issues and that Johnson, Palat, Kucherov, etc are able to cover for him. I expect him to look like himself again next year hopefully after he signs a long-term extension for under 10m