I just look at it as who of the two options would they rather play.
Murray or Djokovic: Federer would rather play Djokovic, while Nadal would rather play Murray. Both got unlucky here.
Del Potro or Davydenko: Federer won't care, as with the form Del Potro is in neither will be a threat. Nadal would prefer to play an out-of-sorts Del Potro. Nadal gets unlucky here.
Verdasco or Soderling: Once again, Federer won't care, as either will be easy for him to beat. Nadal would prefer Verdasco, as he owns him, regardless of surface. Nadal got unlucky again.
All in all, Nadal got the person he would have least wanted to draw in all three picks. Having said that, I still think he'll beat Soderling, and I think he'd have lost to Murray had he drawn him, so the real downer is drawing Davydenko instead of Del Potro. Federer and Murray will cruise through their group, as will Djokovic. I expect the fourth semi-finalist to be the winner of the Nadal/Davydenko match, probably Davydenko.