So far :
- Nadal's, Monfils's and Ferrero's withdrawals are not related to the Olympics
- Verdasco and Wawrinka lost early in the Olympics, we don't know why they withdrew (at least I didn't read that anywhere), that may be an injury, that may be "personal"
- Ferrer I don't know why he withdrew either
and such withdrawals could have happened without the Olympics anyway
if there's a "washout", we will know it in next days only.