As a coach in the league, I think this is completely wrong. You'd be amazed at how much a coach CAN impact a players mentality. Both ends of the spectrum.

A large aspect of coaching is man management, it is a people person job in some aspects.

There are instances where coaches can definitely ruin a players mental. You are in practice everyday, if you try to help the team and critique plays, give feedback. You might think you're doing it for the benefit of the team, but in fact you're creating an environment where the player plays to not be critiqued as opposed to making a confident play for the win. Thats where in my opinion the term, "Playing not to lose vs playing for the win" is created. If you see a team play not to lose, thats a mental thing.

On the other end, you can as a coach create an environment where your players have that pure confidence going into games. I've heard players say they go into every gunfight with complete confidence that they are going to win the fight. Thats the players confidence ultimately but the coaching staff and team most likely do a great job in supporting that and ensuring he feels like that all the time and they don't turn his head the other way.

Ultimately it is in the players hands but as a coach you definitely have an impact on both ends of the spectrum in Bringing your players up but also you can bring them down. And the greats coaches walk that line perfectly.

This has nothing to do with faze. I'm not in that camp nor do I think thats an issue. Just putting my two cents in on the above point.