There's not really a lot to say I guess, it appears Murray needs to work pretty hard on his serve as while he scored more aces than Nadal his first serve percentage was 54% according to the BBC compared to 67% for Nadal and that sort of deficit is difficult to overcome especially when you're playing one of the best in the World. A semi final is still a decent achievement given some of his form this year hasn't been great but it does also have to be said the US Open has been pretty poorly managed too, the lack of a roof there has been shown up as an error which won't be fixed for another few years at least.
I'm hoping the final isn't too affected by rain and presents a great spectacle though.