KEY BISCAYNE: Some fans in the packed stadium shouted encouragement at Roger Federer in Spanish, which is not one of the six languages he speaks.

One man hollered in English, "I love you, Roger!" Another barked, "Get it together."

Words failed to help. In a ragged performance that still produced plenty of drama Tuesday night, Federer lost to Tomas Berdych of the Czech Republic in the fourth round of the Sony Ericsson Open, 6-4, 6-7 (3), 7-6 (6).

"I fought as much as I could," Federer said. "My game has issues at the moment. I'm definitely lacking timing. I don't know where that comes from."

With the upset, the No. 16-seeded Berdych ended a streak of eight consecutive losses against Federer. The 6-foot-5 Berdych also had lost 11 matches in a row against top-10 opponents.

Others advancing to the quarterfinals included Andy Roddick and Rafael Nadal, who could meet in the semifinals.

Roddick beat Benjamin Becker 7-6 (4), 6-3. Nadal defeated fellow Spaniard David Ferrer 7-6 (5), 6-4.

Three-time champion Venus Williams reached the semifinals by defeating No. 6-seeded Agnieszka Radwanska 6-3, 6-1.

The top-ranked Federer won a succession of spectacular rallies to salvage the second set, but he converted only two of 10 breakpoint chances in the match and committed a whopping 62 unforced errors, many on an unreliable backhand.

Grand Slam titles: Federer 16, Berdych 0. Total points in the match: Federer 119, Berdych 119. But Berdych won the last one when Federer sailed a forehand long at 12:16 a.m.

"After a match like that, the feeling is great," Berdych said. "I'm really happy the way I finish it."

Federer held a match point serving at 6-5 in the tiebreaker. But Berdych hit a forehand winner into the corner, then wagged his tongue in relief.

Federer had problems from the start, committing 18 errors to four by Berdych in the first nine games. In a stunning lapse, Federer lost the final eight points of the opening set, double-faulting on set point.

He was twice two points from defeat in the second set before pulling it out, but his shotmaking became more erratic again in the final set. He rallied from a break down before hitting five errant groundstrokes in the decisive tiebreaker.

"It fuels my desire to go to the practice courts, because I don't like to lose these type of matches," Federer said.

The No. 6-seeded Roddick rallied past Becker on the strength of his dominating serve. He dug out of a 1-4, love-40 hole in the first set and won 34 of his final 39 service points, including all six in the tiebreaker.

Roddick said experience helped with the turnaround.

"When things aren't going my way, I'm probably better now," he said. "Six years ago on the court my highs were a lot higher, and the lows were a lot lower. If I would have gotten down early, I don't know if I would have stayed the course."

A big serve helps, too. When Roddick found himself in another hole serving at 4-5, love-30, he responded with three service winners and an ace, all in the 133- to 135-mph range.

"It's nice at love-30 to be able to make some first serves," he said.

Roddick made another one on match point, closing out the victory with his seventh ace of the match and his 343rd of the year, second-most on the tour. He has been broken only once through three matches and on Wednesday plays No. 33-seeded Nicolas Almagro, who eliminated No. 27 Thomaz Bellucci 6-4, 3-6, 7-6 (3).

The woman with the best chance to beat Venus Williams at Key Biscayne watched the women's quarterfinals from the photo pit. Serena Williams had no camera but used her connections to secure a front-row seat as she watched her sister beat Radwanska.

Top-ranked Serena has been sidelined by a knee injury since winning the Australian Open in January. In her absence, Venus has become the woman to beat as she bids for her fourth Key Biscayne title and her first since 2001.

"When I'm executing and playing my best, it's great," Venus said. "It feels good, and I feel like I'm definitely dictating the points and that I don't give my opponent as many chances to have a say."

The oldest women's quarterfinalist at 29, Venus is the hottest player on the WTA Tour. She has won 14 matches in a row, and two more would give her three consecutive tournament titles for the first time since 2002.

In the men's fourth round, American Mardy Fish retired with a sciatic nerve injury trailing Mikhail Youzhny 6-1, 1-0. The injury occurred when Fish took a tumble in the first set, causing discomfort from his back to his calf.

No. 8 Jo-Wilfried Tsonga earned a shot at Nadal on Wednesday night by beating No. 12 Juan Carlos Ferrero 6-2, 6-2. The fourth-seeded Nadal, seeking his first Key Biscayne championship and his first title anywhere in 10 months, punctuated his win over Ferrer with a nifty leg kick-uppercut combination.

The No. 3-seeded Williams hit eight aces and lost only five points on her first serve. She broke five times, including in the pivotal eighth game, when Radwanska had consecutive double-faults and then hit a 62-mph knuckleball serve that Williams pounced on to whack a winner.

Williams' opponent Thursday will be No. 13 Marion Bartoli, who beat No. 12 Yanina Wickmayer 6-4, 7-5.