You seriously believe he's tanking this? You don't think very highly of Murray, do you?
Coming from you that’s hilarious.
But to answer your question since I am also modest, sometimes it's necessary to tank tournaments especially when the big ones are around. If he had won a Slam already, then this wouldn't have been a problem unless he’s really tired, but with the pressure still on, it's only wise as these tournaments are mandatory. So this would be more of a strategic loss if that happens. But if you feel that his level has dropped to the lowest level overnight that he's now losing to a player like Chardy in straight sets, then I question your intelligence and your trust in Andy. But hey.