Error-prone Serena Williams makes quarters at Indian Wells

INDIAN WELLS, Calif. — Struggling with her serve and a rash of errors, Serena Williams overcame a slow start to beat Sloane Stephens 6-7 (3), 6-2, 6-2 in the fourth round at the BNP Paribas Open on Tuesday, extending her winning streak to 14 matches.

Maria Sharapova struggled mightily, too, losing 3-6, 6-3, 6-2 to defending champion Flavia Pennetta, who won her ninth straight match.

Pennetta had 34 unforced errors and just 15 winners. Sharapova topped her in both categories with 42 unforced errors and 27 winners to go with 11 double faults.

Pennetta broke two-time Indians Wells champion Sharapova twice in the final set, winning the last seven games.

Williams committed 52 unforced errors and had nine double faults to go with 13 aces and 31 winners in the up-and-down match played in 90-degree (32 Celsius) heat.

"I'm just trying to find my bearings," the world's top-ranked player said. "Little off this week, but like I said, I'm just happy to be here."

Williams set up match point with a 128-mph ace and won when Stephens dumped a backhand into the net, one of her 36 errors.

Williams broke Stephens three times in the final set of her third match at Indian Wells since ending a 14-year personal boycott of the tournament, where she has won two titles.

"The crowd has been really great," Williams said. "It's been really relaxing here. I just feel I don't want to leave."

Stephens recovered after blowing a 3-1 lead in the first set to dominate the tiebreaker that included just one winner, a smash by Williams to trail 3-2.

Williams has been subdued on court, with none of the screaming and exuberant fist-pumping that often marks her matches.

"That's why I was so calm after I lost (the first set), because it was like, I don't really need to win this title," Williams said. "Just being out here is a real win for me and I was just calm through it."

Stephens won four of the final five points and then promptly got broken to start the second set. Her double faults in the first game set up both break points, and Williams cashed in on the second one when Stephens' backhand went long.

"I had some chances and opportunities that I didn't really capitalize on which I should have," Stephens said. "I was playing the No. 1 player in the world. When you don't take your chances, it could be a little tough."

Stephens held to get to 3-2 before Williams won five straight games to close out the second set 6-2 and take a 2-0 lead in the third. They shared a brief conversation at the net during the post-match handshake.

"I have always thought Sloane can be really great," Williams said. "I think she's on the right track. She played really well. It's good to see her doing really well again."

Williams' fans have not been so gracious toward Stephens, who said last week, "Oh, they hate me."

"I understand that they are die-hard fans and I appreciate that. I'm sure she does, too," she said. "But some of the comments and some of the things are so unnecessary."

Stephens said she blocks anyone on Twitter who writes "mean things about someone else."

In third round men's play, No. 3 Rafael Nadal beat Donald Young 6-4, 6-2 in a matchup of lefties.

"I feel confident that I am playing much better than one month and a half ago," Nadal said. "I feel closer to be what I am, what I want to be, and it's a positive victory for me."

Sixth-seeded Milos Raonic beat Alexandr Dolgopolov, 7-6 (2), 6-4; No. 11 Grigor Dimitrov lost to 17th-seeded Tommy Robredo, 6-4, 1-6, 7-5; Jack Sock upset 15th-seeded Roberto Bautista Agut, 3-6, 6-3, 6-2; and No. 9 seed Tomas Berdych beat Steve Johnson, 6-4, 6-2.

No. 13 Gilles Simon defeated qualifier Michael Berrer, 6-2, 7-5, and No. 27 Lukas Rosol edged Robin Haase, 6-4, 6-7 (4), 7-6 (2).

Roger Federer plays Andreas Seppi at night in a rematch of their Australian Open encounter, when Seppi upset Federer in the third round.

No. 12 Carla Suarez Navarro beat Heather Watson 7-6 (5), 3-6, 6-1 to reach the quarterfinals, where she will play third-seeded Simona Halep, a 6-4, 6-4 winner over 14th-seeded Karolina Pliskova.