Mrs Pessimism here is reasonably confident of this one. I'm pretty sure he wouldn't have lost so tamely to Cilic at the USO if he had not had a problem - as soon as he came out for that match I noticed that he looked troubled and flat.
I'm just a bit worried that he hasn't had an "off" day yet & most players generally have one during a big tournament, so by the law of averages... Still hoping he can pull it off!