Murray is looking very good for a second title at the US Open (barring any stupid **** ups he makes in earlier rounds). Of course Djokovic is the default favourite, but I'm liking the chances of the others to take any of the front runners out. Nishikori, Wawrinka, maybe even Cilic has a good shot at disrupting the order that has reigned for years. Murray should just take CIncinnati easy this week so he's well rested for the Open.
As for Rafa, he's still in a bad place at the moment, but he's a phenomenal previous record to draw strength from. Consider this: despite missing the US Open in 2012 and '14, he has made the semi-final or better dating all the way back to 2008, winning twice. As ever in the slams, if he builds up a good run he gets into dangerous form come the quarter finals, so if he can just get a few match wins in there who knows.