And a delicious prospect loomed: should both advance, they would meet in the quarterfinals.
But Federer could not give New Yorkers the much-anticipated match. He squandered break points against Tommy Robredo of Spain as if allergic to them. He missed forehands by 10 feet instead of 10 inches. He looked very much as he has looked throughout this summer — vulnerable, human, diminished, if only slightly — and he lost to Robredo, 7-6 (3), 6-3, 6-4.
Federer, seeded seventh, had not lost before the quarterfinals at the United States Open since David Nalbandian beat him in the fourth round in 2003.
The cracks started to show in the first-set tiebreaker. With Robredo ahead, 4-3, Federer hesitated, then charged for a late approach shot. Robredo returned low, and Federer clanked a backhand volley into the net. Stranger still, he charged the net again on the next point, as if he wanted to end it quickly, and Robredo clocked a forehand winner and took the set on the next point.
In the second set, Federer played even worse. He managed six break-point chances in the set. He converted none of them.
“I almost don’t believe what I’m seeing at times,” the commentator John McEnroe said on the ESPN broadcast. “It’s not that he’s missing it. It’s the lengths he’s missing it by, the amount.”
Early into the third set, Federer went up by 0-40 on Robredo’s serve. More break points. More missed chances. He shanked a forehand. Robredo passed him.
It was another night to add to Federer’s struggles, to the second-round defeat at Wimbledon, to the semifinal loss in Hamburg and the second-round fall at Gstaad, three losses that came against players ranked outside the top 50. Robredo, at least, was seeded 19th here. But Federer had owned him until Monday.
Federer had hoped to return to his old form in New York. In the early rounds, he attacked more, volleyed more. Federer, a five-time Open champion, had started to give fans reason to believe he could contend once more. He did not lose a set in his first three victories. His third-round victory lasted 81 minutes.
As a fan I don't know what hurt more reading the result, or actually watching it on tv (which was torture). 
I think the loss would have been better to stomach (if there even is such a thing) had Federer played better. 
Fought back a little more, but most importantly taken advantage of all the squandered break points.  Not to mention countless other opportunities on his own serve.
Once again we were denied the first ever meeting of Fedal in the U.S. Open quarter-finals. But in all honesty even if Federer had somehow pulled off a win and reached it, with play like that he would have no chance anyway.  
Better he lose to a lesser quality player, then another heart-break and overwhelming head to head win for Nadal.
Still as a die hard fan, would have been nice if Federer had been given a chance to try anyway.  
But this time he really does have only himself to blame, because as he said in the post match interview he self destructed (in a pretty epic fashion).

Also not looking forward to (will try my best to avoid) the "Roger is slowing down, getting older, lost a step" comments that are sure to come from this loss courtesy of the sports media.
Instead I hold on to this bit of post-match quote from the man himself:

 "So I've definitely got to go back to work and come back stronger, you know, get rid of this loss now as quick as I can, forget about it, because that's not how I want to play from here on. I want to play better. I know I can. I showed it the last few weeks, that there is that level".
All your fans believe that too Roger, we believe that too.
Now if you'll all excuse me, I'm going back to my sulking (since the screaming and crying part is done).