Did he say this particular performance can be attributed to him playing the Olympics? No it if YOU I choose not to believe.
What he said was that because of the Olympics he did not get to do his usual training block in Miami after Wimbledon.
This is the training block he does where he acclimatises to the hot, humid conditions ready for the US hardcourts by doing sprints, hitting the gym and piling on muscle to sustain him through this part of the season.
This year he spent that portion of time in cool damp London and this is impacting his ability to deal with the conditions out there. This makes sense, it was evident in R1 and it was clearly evident out there today. In past years with his normal schedule he has handled this sort of condition far far better.