Five things we learned from the long weekend

1. Fed's in the groove: Roger Federer passed his first test: his straight-sets demolition of dangerous Czech Radek Stepanek on Sunday, warranting an "A." Stepanek won their previous match in May.

Federer served huge, notching a percentage of 71, and added 12 aces. The pro-Federer crowd became even more excited when their man unleashed a leaping overhead from behind the baseline that fooled Stepanek and landed in.

The 96-minute rout was a far cry from his form in the first two rounds. In Federer's defense, it can't be that easy getting motivated facing Maximo Gonzalez and Thiago Alves.

"It's good for me not to waste any energy," Federer said. "I'm playing well."

Not good news for the rest of the field, including Tuesday's fourth-round opponent, Igor Andreev. Even with his big forehand, the Russian shouldn't trouble Federer.

"If you look at it as a comparison between two cars, one car is just better," Dmitry Tursunov, Andreev's buddy and Davis Cup teammate, acknowledged. "As long as the driver can mess up, anything can happen. But I can't imagine Roger's going to play atrociously. It's one dimension versus 67 different dimensions."

2. Fairy tales can come true, it can happen to Gilles Muller: Down on his luck -- and to his last few bucks -- Gilles Muller thought about retiring.

He decided to keep going, then almost skipped the U.S. Open because he arrived late from Europe. The misses continued in the first round of qualifying, as Luxembourg's most prolific men's pro -- even the 25-year-old admits that doesn't mean much -- survived a three-set battle.

In the main draw, Muller, a former junior No. 1 now ranked 130th, came back from two sets down to win in the second round against Tommy Haas, no stranger to success at the Open and once the world's second-ranked player.

In the third round, Muller repeated the feat against Spanish 18th seed Nicolas Almagro. He can't quite believe how the tale is unfolding himself, especially since he's spent most of 2008 in the second tier.

"The whole year already I was only playing Challengers, and I was fighting to win some matches there," he said. "Now I'm here, I went through qualies, and I'm winning three matches in the main draw. It's tough to realize, actually."

Muller won't want to give fifth seed Nikolay Davydenko a two-set head start in the fourth round.

3. Men's matches do go five sets: Usually filled with a few action-packed encounters in the first two rounds -- involving seeds, that is -- the men's proceedings lacked a certain bite this year.

The weekend made up for it.

There were no fewer than five five-set thrillers, with no blowouts in the deciding set, either. Three featured rallies from two sets down.

Like Muller, Andy Murray was two points away from defeat in a third-set tiebreak. The fiery and fast-rising Scot showed his muscle, literally -- flexing his bicep when the match ended -- to overcome unpredictable Austrian Jurgen Melzer.

Japanese teen Kei Nishikori, praised in the past few months by both Federer and No. 1 Rafael Nadal, knocked off a slumping David Ferrer, despite almost blowing a two-set advantage.

The other Swiss, Stanislas Wawrinka, and the in-form Juan Martin Del Potro were the other victors. Wawrinka needed four hours, 14 minutes to top Italian journeyman Flavio Cipolla in an ill-tempered tussle.

Cipolla refused to shake Wawrinka's hand, miffed that Wawrinka cheered his double faults and replicated his limping on court. Wawrinka accused Cipolla of faking it.

"After each point he lost, he was acting like he was dead," Wawrinka complained.

4. The Russian women are still rolling:
There's no stopping the Russian juggernaut of Elena Dementieva and Dinara Safina, the Olympic gold and silver medalist, respectively.

Dementieva cast aside her own fears she'd struggle with motivation following her exploits in China. On Sunday she captured a straight-sets win over her toughest opponent yet, China's Li Na, the fourth-place finisher in Beijing. Taking advantage of a comfortable draw, the oft-smiling Dementieva hasn't dropped a set yet.

"I don't feel I'm playing my best, but it's good to [know] that I have slowly improved my game with every match," Dementieva said. "Hopefully, once again I can play better the next round."

Safina, the most prolific player on the women's tour this summer, hasn't been much worse. She dropped her first set Saturday against Swiss Timea Bacsinszky, only to crush German Anna-Lena Groenefeld on Monday.

Safina didn't think she would beat Groenefeld because she was "exhausted." In tears before the match, she was eventually calmed down by her coach, Zeljko Krajan.

"I just went on court and said, 'OK, I'm going to [see] what I can do today,'" Safina said. "And slowly I started to feel like, 'OK,' like I can push myself."

No matter how tired, it's difficult to envision Safina losing to Italian Flavia Pennetta in the quarters. One of the Williams sisters lurks in the semis.

5. Rafa is, yes, human:
So Rafael Nadal lost a set and looked fragile at times in a 6-2, 5-7, 7-6 (2), 6-3 win over big-hitting Californian Sam Querrey on Monday. It had to happen sometime, even if he is the most dominant player around.

Nadal coasted in the first set and was up 5-3 in the second before a match broke out, as the Spaniard dropped the next four games.

The world No. 1 blew another break lead deep in the third set and was forced to go to a tiebreak, as Querrey let it rip from the baseline, mostly doing damage with his forehand. At 4-2 up in the fourth, Nadal needed to save seven break points.

"It was very difficult, especially after my big mistake in the second set," said Nadal, who's trying to end Federer's four-year reign at the Open after dethroning him at Wimbledon. "I was playing normal, fine. Nothing special, nothing bad. I had the match under control, no?"

The inevitable questions about his fitness surfaced following a grueling past five months. His latest pit stop was in Beijing, where he claimed Olympic gold.

"Well, if I don't feel recovered after two weeks, we have a big problem," Nadal said.

If Nadal downs another American, Mardy Fish, next, he'll find himself in a U.S. Open semifinal for the first time.

Ravi Ubha is a frequent contributor to ESPN.com.