Legally? They can't make you play. If you don't want to play, you don't have to play. But you can't as a player make them trade you, and you of course don't get paid if you sit out. So you're gambling that the team blinks before you do.
That the player made his drunk ass pops delete the tweet says everything there is to say about how credible it is, though. It's exactly what it appeared to be: An emotional social media post by someone adjacent to the player, not the player himself.
His father probably only speaks for himself, and has no doubt already been instructed to avoid speaking for his son again.