Facing his first lefty (other than Nadal) in more than a year, Roger Federer struggled to figure out Feliciano Lopez's supersonic serves and laser-guided forehand in the fourth round on Monday night. But at 0-40 in the first game of the third set, R-Fed found his mojo.

Federer ultimately won the match, 3-6, 6-4, 6-1, 6-4, and set up a quarterfinal rematch with his opponent from the 2006 US Open final, Andy Roddick.

“I had to struggle, really,” Federer said of the first two sets. “He was going for it. He was serving 110- to 115-mph second serves, taking chances.”

A little more than an hour into the match, tied at one hard-fought set each, Federer served the first game of the third set, and not only saved three break points to win that game, he broke Lopez in the next game, and went on a tear by shrewdly accumulating 17 consecutive points on his own serve to capture the set, 6-4.

But that wasn't all.

In the fourth set, Federer broke Lopez in the first game then completely blanked the 60th-ranked Spaniard whenever he had a chance to serve – ultimately extending his streak to 33 consecutive points without losing a point on serve.

It wasn’t until the end when Federer – for a brief moment – started to look human again. Leading 5-3 in the fourth, with Lopez serving 0-40, Federer squandered three match points – sending the first two into the net. Then, at 5-4, with a chance to serve out the match, the three-time US Open champion finally relinquished a point on his serve (ending his streak at 35) as Lopez made it 30-15. Federer quickly regrouped and won the next two points – including a gentle forehand down the middle to send the Spaniard packing.

Federer has a 13-1 record against Roddick, his quarterfinal opponent.

“It’s a great record. But it doesn’t help me,” Federer said. “We’ll see how it goes. It’s a new day. Anything’s possible.”