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. The only difference between the two tricks is that what Murray is doing takes a little longer to work (few games, or even a set), while medical timeout can have an immediate effect, unless the opponent is a true pro and blocks it out. 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.