NEW YORK – For two sets against Roger Federer at the U.S. Open, Andy Roddick was very good, quite possibly as good as he can be.

For two sets, Mr. Roddick banged big serves at up to 146 mph, collecting aces and service winners and never double-faulting, never facing a break point.

For two sets, he conjured up groundstroke winners, strong volleys, impressive returns.

And what did all of that superb play last night earn Roddick? A two-set deficit and, eventually, a 7-6 (5), 7-6 (4), 6-2 loss in the U.S. Open quarterfinals, a round or two earlier than Mr. Roddick is accustomed to succumbing to Mr. Federer.

And accustomed Mr. Roddick most certainly is, dropping to 1-14 against the man who replaced him at No. 1 in the rankings 3½ years ago and has been there since.

“I mean, I’m not walking off with any questions in my head this time. I’m not walking with my head down,” Mr. Roddick said. “I played the right way.”

Mr. Federer, though, reached his record 14th consecutive Grand Slam semifinal thanks in part by being barely better in each tiebreaker.

The last two men’s quarterfinals were scheduled for today, with No. 3 Novak Djokovic playing No. 17 Carlos Moya, and No. 15 David Ferrer — who upset Rafael Nadal in the fourth round — taking on No. 20 Juan Ignacio Chela.

Mr. Federer, meanwhile, will face No. 4 Nikolay Davydenko in Saturday’s semifinals. Mr. Federer is 9-0 against the Russian — and knows that full well.

“I’ve got a pretty good record against him. Never lost,” Mr. Federer said. “But let’s not get ahead of ourselves.”

Well, looking ahead a bit, a victory over Mr. Davydenko would put Mr. Federer in his 10th straight Slam final, adding to another record. And if Mr. Federer can hoist the trophy Sunday, he would become the first man since the 1920s to win the American Grand Slam four years in a row.

He also would up his major title total to 12, trailing only Pete Sampras, who collected 14.

Mr. Roddick is still stuck on one Slam, the 2003 U.S. Open, and has lost all six times he’s faced Mr. Federer at majors. That includes last year’s U.S. Open final.

So does Mr. Roddick think he can beat Mr. Federer?

“Yeah,” he said. “If I didn’t, I wouldn’t be out here.”

Early in yesterday’s match, Mr. Roddick stayed right with Mr. Federer, even strutting a bit while buoyed by a sellout crowd of 23,733 and yells of encouragement from his coach, five-time Open champ Jimmy Connors, who wore a jacket and tie for the occasion.

After holding to 4-4 in the first set with a 138 mph ace, Mr. Roddick stared down his familiar foe and bellowed. Watching from up high in the USA Network booth, Andre Agassi saw that show of emotion and sounded a word of caution.

“There’s a fine line,” the eight-time major champion said, “between getting pumped up and waking a sleeping giant, I assure you.”

Sure enough, when it mattered the most, Mr. Federer was wide awake.

“I know that I have a big repertoire of shots and things I can choose from,” Mr. Federer said. “I’m happy the way I’m maintaining this great ability of coming up with the important wins when I have to. I’m at my best always at the Slams.”

There were zero breaks of serve in the first two sets, but Mr. Federer came through in the clutch.

With Mr. Federer ahead 5-4 in the first tiebreaker, Mr. Roddick smacked a 130 mph serve that Mr. Federer got back. Mr. Roddick charged the net behind a good approach shot, but Mr. Federer flicked a cross-court backhand passing winner, leaving the American cursing.

At 6-5, Mr. Federer hit a 122 mph ace and slowly punched the air to celebrate while Mr. Roddick muttered to himself.

It was almost the same in the second tiebreaker. At 4-4, Mr. Roddick unleashed a 140 mph serve, and Mr. Federer conjured up the shot of the match, a reflex backhand return that put the ball right at the opposite baseline, near Mr. Roddick’s feet. Mr. Roddick couldn’t handle it, and two points later, Mr. Federer’s 128 mph service winner put him ahead by two sets — and sent many in the stands streaming for the exits.

How different things could have been.

As Mr. Federer noted, matter-of-factly: “I could have been down two sets to none.”

Instead, he finally earned break points while up 3-2 in the third and converted the second. Did the same at 5-2.

And that was it.
“

It was a very high-standard match. I was very pleased with my performance,” Mr. Federer said. “I thought actually Andy also played very well.”

Then came the scariest thought of all: Mr. Federer figures he can get better — and will work to do so.

“It would be nice,” he said, “if I improve.”

Nice for whom, exactly?