Although he did defeat Del Potro at the U.S. Open, and that's because Del Potro's skill level wasn't as good as Murray's yet.
it never was
But almost all the players I mentioned above crushed him with power games at the slams. Murray's accurate forehand works on lower level ranked players, and 1 dimensional players. But against players with massive forehands, he'll have to come with a lot of accuracy and a ridiculously strong defense to survive at the slams.
nobody crushed him, I think they all have got a bad record against him.
oh yeah, it only works on lower level and one dimensional players such as federer, good point.