He didn't beat Rafael Nadal.

It is undeniable that Federer was at his best in the U.S. Open final, whipping the ball around the court in every direction and running a wide-eyed Andy Murray ragged. His level of play seemed unbeatable, but still there's that big elephant in the room.

Sure, Murray beat Nadal — handily. And Federer, in turn, beat Murray — handily. But the transitive property does not apply to professional sports, and in a game that loves its rivalries, something was definitely lost at Arthur Ashe Stadium on Monday with Nadal sitting it out.

And Federer knows it. He was asked after Saturday's semifinal win whether he'd prefer to play Nadal or Murray for the title.

"I guess I prefer Rafa because we have played so many times and we had such a great Wimbledon final," Federer said after beating Novak Djokovic.

"After what we went through at Wimbledon and all the tough matches we have had over the years, it's just always nice to play against him."

At the '07 U.S. Open, this wasn't an issue. Federer had been so singularly dominant the previous four years, all that mattered was how easily he would cruise to glory. He rolled through Grand Slam events as though they were practice sessions, and we sang his much-deserved praises. Even when he lost in the French Open year after year to Nadal, we brushed off Roland Garros as the black sheep sibling of the other majors.

When Nadal beat him at Wimbledon in July, all that changed. It gave him a nemesis. He finally had the Agassi to his Sampras, the McEnroe to his Borg.

The ensuing chain of events has left Federer with a strange-looking "2" next to his name in every tournament draw. The near-invincible Swiss has suddenly become more interesting. He's vulnerable. He's beatable. He's human. The only thing left to do was get revenge against the guy who knocked him down a peg.

Federer's 6-2, 7-5, 6-2 win over Murray was — in terms of total games dropped — his second most dominant win in a Grand Slam final, and Murray was the only of his 13 title-match victims who didn't at least force a tiebreak in one of the sets. It's a far cry from July's five-set Wimbledon classic, where he and Nadal slugged it out until almost complete darkness.

That match validated Nadal's ascendance. Federer needs no such validation. He has 13 of the sport's most coveted prizes. But his legacy will be incomplete without one more Grand Slam win against the only man to force him to accept a runner-up trophy at a major championship.

Serena's the one ... for now

Serena Williams is back at the top of the rankings after winning her third U.S. Open title, the first time since August 2003 she's been No. 1. She left very little doubt in the process.

The younger Williams sister didn't drop a set and won 6-2 or better in eight of the 14 she played. The only player who made her sweat was Venus, who forced Serena to win two tiebreaks in their quarterfinal match.

We'll see how long it lasts. The last time she attained the No. 1 ranking — after winning Wimbledon in 2002 — she was in the process of taking four straight Grand Slam titles. But after another triumph at Wimbledon in '03, she only won one Slam in the next 13 tries.

The top spot has been a revolving door since Justin Henin's retirement in May. Maria Sharapova, Ana Ivanovic (two different times), Jelena Jankovic and now Serena have all held it since then as the WTA Tour enjoys a period of parity at the top.

Second serves: Federer needs Nadal rematch Zack Pierce / FOXSports.com 121 days ago   He can't control it. It doesn't ruin his moment. They won't put an asterisk on his trophy. But Roger Federer's latest Grand Slam title comes with one inescapable caveat. 2008 U.S. Open U.S. Open Central Results: | Murray wins | | Men | | | Women | | | Men | | Men Day 4: Ivanovic ousted | 3: Men | Women Day 2: Men | Women | | Analysis: Cronin: Federer's back in the mix Pierce: One thing missing for Federer Cronin: Serena's hard work pays off Others: PHOTOS: Men's final | Women's final | Day 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 PHOTOS: U.S. Open fashion Singles draws: Men's | Women's Results: Men Women | Ranks | Schedule Partners: Tennis Week: Analysis, video and more Richard's Court: Inside the tennis world

Nothing against Mardy Fish, but when he's the most compelling American at the U.S. Open ... it's not the best sign. (Matthew Stockman / Getty Images)

American mess

Immediately after Federer's post-title ceremony concluded, CBS strapped us into the time machine and showed us the final points of the last final to feature two Americans — in 2002, where Sampras beat Andre Agassi for his 14th and final Grand Slam title.

It was a fitting segue to follow the coronation of a man who will soon tie that record, but it also served as a reminder of the state of American tennis. Mardy Fish routed ninth-seeded James Blake in Flushing Meadows. Eighth-seeded Andy Roddick made it as far as his rank dictated, clearly overmatched by No. 3 Novak Djokovic in the quarters despite the urgings of the New York crowd.

We haven't seen three straight years without an American in the U.S. Open final since the late 1980s, when Ivan Lendl and Mats Wilander ruled the roost. Without much hope for the immediate future, that streak seems likely to be snapped in 2009.

Zack Pierce is a senior editor for FOXSports.com.

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