Plenty of players play singles and dubs, he'll be fine.
Yes, but playing (potentially) back-to-back (to-back) 5 setters takes its toll on the fittest of players ... and it is unclear (despite Vasek's comments) if he is up to the task after his bout with mono. And Vasek seemed to be showing slight signs of fatigue in the 3rd set already yesterday ... I just had the feeling on that late break chance he had in the 3rd that it was "now or never ... you lose this set & match is over" ... and it was.
I'll get off my soapbox now on this .. really hope I'm wrong and Vasek comes out strong today to help take the "decisive" doubles (Milos will up his game tomorrow after so-so performance against the Fog) .. and everyone here can say an emphatic FAIL to my pessimism (I might even do that to myself :-) ).