Denis Istomin upsets David Ferrer at Indian Wells

Fifth-seeded Spaniard David Ferrer exited the Indian Wells Masters ATP-WTA event on Tuesday after losing his third-round match to Denis Istomin 6-4, 6-3.

Ferrer, who had won three titles already this year, suffered just his second loss of 2012 to go with 19 victories. He won tournaments in Auckland, Buenos Aires and Acapulco.

Istomin broke Ferrer in the opening game then won the final five games of the match, breaking Ferrer three times in the second set.

Uzbekistan's Istomin, ranked 51st in the world, fired five aces and won 80 percent of his first-serve points.

Ferrer finished with five aces, three double faults and won just four of 15 points on his second serve in the 74-minute match.

Istomin advances to the fourth round, where he will play Argentina's Juan Martin del Potro.

Istomin reached the final of the San Jose tournament last month, losing to Canadian Milos Raonic.

Del Potro survived six set points en route to a 6-2, 7-6 (8/6) win over Fernando Verdasco on Tuesday.

"Verdasco is really difficult opponent, especially in the beginning of the rounds of the big tournaments," del Potro said. "He's very, very tough, very dangerous, and I think I made a good match."

Del Potro is also off to a roaring start this year, having made the quarter-finals or better at every tournament he has played.

Del Potro survived four set points in the 10th game of the second set against Verdasco before closing it out in the tie-breaker.

Del Potro hit four aces, won 71 percent of his first serve points and saved all six of his break-point chances.

"In the tiebreak he made the double fault to give me first match point. I get the opportunity and I take it," del Potro said.

Thomaz Bellucci of Brazil advanced in a walkover when Russian Nikolay Davydenko pulled out with a virus.

Davydenko is the latest in a string of ATP and WTA players to withdraw or retire from matches complaining of a flu bug that has swept across the Palm Springs area.

Former French Open winner Francesca Schiavone and reigning Wimbledon champion Petra Kvitova withdrew Monday with stomach illness.

On the women's side of the draw, top seed Victoria Azarenka extended her win streak this year to 20-0 by beating Julia Goerges 6-3, 6-1 in the fourth round on Tuesday.

Azarenka advances to the quarter-finals where she will play number five seeded Agnieszka Radwanska.

American Jamie Hampton had to retire from her fourth-round match with a cramping problem, allowing Radwanska to become the first player through to the quarter-finals.