Updated: March 29, 2010, 10:05 PM ET

Federer ousts Serra; Kuznetsova falls

Associated Press

KEY BISCAYNE, Fla. -- Thrusting a clenched fist toward the far end of the court before the final point, Venus Williams telegraphed her intentions.

Her next shot packed plenty of punch: a 121-mph serve that handcuffed Daniela Hantuchova, who avoided injury but was unable to put the ball in play.

With that, Williams won 1-6, 7-5, 6-4 Monday to reach the quarterfinals of the Sony Ericsson Open. She trailed almost the entire match and then surged across the finish line, winning the final seven points.

"I was a little bit off and struggling to find the court," the No. 3-seeded Williams said. "Of course I'd like to win more straightforward, but when it counts and times get tough, I always feel confident that I'm going to find a way to win."

She did that in the last game. Williams smacked service winners on the first two points, then yanked a screaming forehand cross court past a lunging Hantuchova, which prompted the fist pump. Then came the clinching serve.

"I'd like to play every game like that," she said. "It was a perfect game."

While Williams averted an upset, top-seeded Svetlana Kuznetsova and defending champion Victoria Azarenka lost. No. 2 Caroline Wozniacki beat No. 22 Anastasia Pavlyuchenkova 6-2, 6-2.

The lone American woman to reach the final 16, Williams seeks her fourth Key Biscayne title, but her first since 2001. Her quarterfinal opponent will be No. 6 Agnieszka Radwanska, who beat Yaroslava Shvedova 6-1, 6-4.

Like Williams, top-ranked Roger Federer endured some wobbly stretches before beating Florent Serra 7-6 (2), 7-6 (3). Federer lost serve three times, each time when he led, and committed 35 unforced errors to 32 for Serra.

But Federer won eight consecutive service points in the tiebreakers and closed out the victory with a service winner to reach the fourth round.

"All in all, I'm thrilled to be through," he said. "At the end of the day, that's what counts."

Spectators for his match included Rafael Nadal, a potential opponent in the men's final Sunday. They last met 10 months ago in Madrid.

"It has always been a lot of fun playing against him," Federer said. "I hope that day is going to come soon again."

Mardy Fish advanced with his second consecutive win over a seeded opponent, beating No. 29 Feliciano Lopez 7-5, 6-3. Fish upset defending champion Andy Murray in the second round.

No. 16 Tomas Berdych beat Horacio Zeballos 6-4, 7-5 and will play Federer next.

Former No. 1 Kim Clijsters beat Azarenka 6-4, 6-0. Clijsters, seeded 14th, next plays No. 9 Samantha Stosur, who eliminated No. 7 Jelena Jankovic 6-1, 7-6 (9).

Kuznetsova struggled with a right shoulder injury and lost to Marion Bartoli 6-3, 6-0. Kuznetsova, the 2006 champion, required treatment from a trainer three times during the match and won only eight points in the second set.

"I almost had stars in my eyes, it was so painful," Kuznetsova said. "I cannot return. Then I cannot serve."

The upset was nothing new for the 13th-seeded Bartoli, who has won seven of her past 11 matches against top-five players.

Beating Hantuchova is nothing new for Williams, who has won all 10 of their matches. The latest was by far the closest, beginning in sunshine and finishing under the lights.

Williams committed 45 unforced errors, including 11 as she lost the first four games. Her backhand was especially unreliable, and the match was nearly two hours old before she took a lead.

"Days like this, you just have to figure out a way to win the point, even if it's not pretty," she said. "I enjoy that battle."

Despite her struggles, Williams won her 13th match in a row, and she improved to 45-8 at Key Biscayne. Only Steffi Graf and Serena Williams have won more matches in the tournament.

Federer ranks third among the men at 36-9, trailing only Andre Agassi and Pete Sampras. Federer won the title in 2005-06.