Murray does play mind games, just like the other top guys. His main trick is to give impression to his opponent that he is struggling, that he is physically exhausted. How many times have we seen Murray grab his back, or his knee when he loses a point? Then when he wins a point and he's fine. Few minutes later he loses a point and he starts grabbing his knee/back again.
It's VERY tricky to play an opponent who is REALLY either injured or physically tired. When you play someone who looks injured, your natural instinct (conscious and/or sub-conscious) is to lower your game, to play safer, to make him run. Why go for the lines, red-line your game when your opponent is struggling, right? Wrong! Murray is not injured, he is not tired, he just wants you to think he is, so that you lower your standard of play, and then he strikes. Once you lower your standard of play, it's very difficult to raise it. Momentum is gone, confidence is gone, and you start making errors you were not making few games earlier. Nothing wrong with that trick imo. If you as a player, as a pro, allow yourself to be manipulated like that, you deserve everything you get, and you're not a pro (in that match at least) no matter what your ranking says.
Murray's tactic is no different to Nole or Rafa taking a medical timeout. Both tricks serve the same purpose: to destroy your opponent's rhythm, his confidence. To swing the momentum back in your favor. Once the momentum is gone, there is no going back. These top guys are almost impossible to stop once you give them back the momentum, especially against lower ranked opponents.
Pros are impermeable to mind games.
This is a joke. No, there is clear difference between an involuntary tic and clearly deciding when you opponent is a on a roll to delay play to check out the tape on your knee.
More often than not when Murray is grabbing himself, he does not play any better or worse, nor does his opponent, he can do it when he's winning and still win, and when he's losing and still lose.