NEW YORK -- They say the definition of insanity is doing the same thing over and over and expecting a different outcome. The definition of tennis insanity is failing to take advantage of those rare opportunities to pick Roger Federer's pocket and hoping to come away rich.
Federer systematically drove James Blake crazy the first four times they met, teasingly allowing Blake to stay close in at least one set per match, then yanking the momentum and the result back like a benign bully playing keep-away. Going into Thursday night's U.S. Open quarterfinal, the fifth-seeded Blake had yet to win a set from the world No. 1.
Blake let a first-set tiebreak skitter off his strings, then came back from a two-set deficit to wrestle the third from Federer in an excruciating 11-9 tiebreak. He made the Swiss superstar toil through three match points in the final set, but in the end, Federer kept his hand firmly on his wallet and the chance to win a third straight Open title.
Federer seemed slightly disoriented after the 7-6 (7), 6-0, 6-7 (9), 6-4 quarterfinal victory that propelled him into Saturday's semifinals against seventh-seeded Nikolay Davydenko of Russia. He grinned and let his tongue loll out of his mouth in apparent relief.
"It took a while today," Federer said, shaking his head as he was interviewed on the court after the match.
Later, in his post-match news conference, Federer called the match "unbelievable high quality," and added, somewhat superfluously, "For me, it takes a lot to come out and say this match was unbelievable, you know."
Davydenko is 0-7 lifetime against Federer, losing most recently in the Australian Open quarterfinals, where he pushed Federer to tiebreaks in the final two sets.
"He's really improved a lot on hard courts," Federer said. "We all knew he could play on clay. All of a sudden he kind of found another gear, more confidence from the baseline. [He's] also incredibly fit, you know, never breaks down. Has the much bigger belief now than he used to have."
The Russian will need all of that against Federer, who tied Ivan Lendl's Open Era record by reaching his 10th consecutive Grand Slam semifinal. Just ask Blake.
"To a certain extent I take pride in the way I fought," Blake said. "I almost did it. I didn't play my absolute best, but he probably didn't either. It's a good feeling to know that I'm close to Roger. A wise man -- or, well, maybe not a wise man, just Todd Martin -- told me if you win one set, you can win two. If you can win two sets, you can win three.
"I was one point away from winning [the] first set, too. I guess he's human."
Blake struggled for traction in his second service game of the match, enduring seven deuces before he finally dug in to go up 2-1. Federer went ahead 5-4, breaking Blake at love with a snappy stop volley well behind the service line, but Blake was able to equalize in the next game.
Federer shot to a 4-1 lead in the tiebreak before Blake reeled off five consecutive points and suddenly found himself on the brink of wrestling his first-ever set from Federer. But the relentless champion thwarted him on three set points, uncorking an ace, inducing Blake to swat a forehand long and smack a return into the net. Blake's final return nicked the net tape and bounced wide.
The second set unraveled quickly for Blake, who called it "an old-fashioned whipping."
Federer said he surprised even himself with his level of play.
"Maybe he, you know, let his head hang a little bit, but I took advantage of every chance I got there and actually raced through," he said. "Maybe that second set was more important than the first."
But then Blake deviated from the usual script. Down two sets and a break at 5-3 in the third, urged on by a suite full of bullhorn-voiced friends from his hometown of Fairfield, Conn., he lashed a forehand crosscourt winner on break point to get the set back on serve.
Federer hadn't dropped a set in the tournament until he lost his grip in Thursday's taut third-set tiebreak. Tied at eight points each, the two men engaged in a 30-stroke rally that ended with Blake dumping a forehand into the net.
The world No. 1 then had a match point on Blake's serve, but Blake hit a sizzling backhand passing winner to deny him.
Blake hit a forehand winner to go up a point, then cracked a backhand half-volley on his fifth set point. Federer slipped as he cranked up to respond with a backhand -- an unusually clumsy moment for the smoothest player in tennis -- and fell to his knees as he mishit the ball.
Unfortunately for Blake, Federer responded to that setback in his typical maddening manner, playing on without a hint of panic. "Did his heart rate ever go up above about 60?" Blake asked rhetorically as he gobbled a post-match snack.
"It wasn't just a walk in the park for him, I'd like to think. I definitely feel like I let him know that I can play. He is legitimately a level above me right now. That's not to say I can't beat him on a given day, but there's definitely work to be done and I need to play better if I expect to be on that level consistently."
Frequent contributor Bonnie DeSimone is covering the U.S. Open for ESPN.com.