Andy will just have to be tough skinned or just not pay any attention to the commentators. It seems to me that these people just blah blah blah and don't even think about what comes out of their mouths.
I hope Andy is okay, it was cool when he played yesterday which could have had an affect on his back. With the tough tennis these guys are all playing, he needs to be able to play as tough.
He's kept himself in good shape for such a long time, must be the hard work that Lendl expects of him that has maybe caused this injury.
Good Luck Andy, hopefully it will be warm and the sun will warm your back, and you will not have any more spasms. Should you play tomorrow, may the force be with you Mr Magic!!