Fed didn't give any excuse after the match you worhtless troll,now go back to your cave and stay there.
Well, that's not completely true:
From FSN:
Federer made clear afterward he was not pleased that play continued despite the low visibility at the end
"It's rough on me now, obviously, you know, to lose the biggest tournament in the world over maybe a bit of light," he said.
Maybe not completely an excuse, but he seems to be saying that if it had been lighter, he would have won.
Fed did give a lot of credit to Nadal in the presser afterwards, but the light comment is pretty lame.