Milos Raonic remains the last Canadian standing in singles action at the Sony Open after beating American Jack Sock 6-4, 7-6 (7-1) on Saturday Key Biscayne, Florida.

Fellow Canadian Vasek Pospisil is out of the tournament following a loss in his debut match.

Raonic, seeded 12th, hung Sock out to dry in their second-round match, ending with his 14th ace after 86 minutes. The Thornhill, Ont., native broke once while allowing Sock few chances to take an initiative.

"It was a decent first match, a bit windy," said Raonic. "It was a good chance to find my rhythm.

"The further I get into a tournament the more I start to cut my margin for error. I think in the next match (against Spain's Guillermo Garcia-Lopez) I can start to take more chances."

Raonic's victory marked his third straight appearance in a Miami third round, the best he has done so far. A year ago, he was forced to withdraw with an injury before facing American Sam Querrey.

Toronto doubles veteran Daniel Nestor and Serbian partner Nenad Zimonjic took an opening win over Andy Murray's elder brother Jamie Murray and John Peers, beating the pair 6-4, 7-5 in the first round.

Pospisil failed to end a two-month losing streak on the ATP as the Vancouver native fell to Slovenian Aljaz Bedene, but came away with a positive attitude on his progress after recent back pain.

The 27th seeded Pospisil was beaten in a first-time meeting with Bedene 7-6 (7-5), 5-7, 6-3. Pospisil, only recently recovered from pains which began late in the previous season, won the opening set but could not maintain momentum.

He had never played the Masters 1000 event in South Florida.

Pospisil went down in just under two and a half hours, and has not won a match since the Australian Open in mid-January when he beat Matthew Ebden in the second round.

"Overall it was positive for me," said Pospisil, "The back felt almost 100 per cent. It was the first time I felt I could compete and have a chance of winning a match."

Pospisil ended with a modest seven aces against eight for No. 119 Bedene, with Pospisil never earning a break point while losing serve twice.

"It was a tough match. He played well, it was very physical," Pospisil said. "My level fell a bit at the end when I needed to hang tough, but it's a good feeling knowing that you can compete.

"I felt that I could almost move up to my standards. It's a much better feeling. I'm disappointed but I did play well, especially on serve and from the back of the court."

Sharapova, Williams survive marathons

Maria Sharapova needed nine match points before she finally closed out a win Saturday in the third round of the Sony Open, beating Lucie Safarova 6-4, 6-7 (7), 6-2.

No. 1-ranked Serena Williams won a marathon, too, taking 2 1/2 hours to eliminate Caroline Garcia 6-4, 4-6, 6-4. Men's No. 1 Rafael Nadal began a bid for his first Key Biscayne title by beating Lleyton Hewitt 6-1, 6-3.

Sharapova had two match points in the tiebreaker, and seven more in the final game. The No. 26-seeded Safarova stayed alive with a succession of vital winners.

"She kept hitting unbelievable shots," Sharapova said. "One more. One more. I said, 'How many chances are you going to get?"'

With the capacity crowd in a frenzy, a long exchange on the final point ended with Safarova pushing a weary forehand into the net. She then shared a hug with Sharapova.

The match took three hours and ended at 10 p.m. to conclude an 11-hour day session on the stadium court, with two night-session matches yet to come.

"After a match like that, it's tough to have only one winner," Sharapova said, "because both players give a lot and both want to win so much."

Williams' match was a thriller, too. A succession of long rallies left her grunting, stumbling, lunging, squealing, flailing her arms and scolding herself.

Despite all the drama and trauma, she moved one round closer to a record seventh Key Biscayne title.

Williams is playing in her first tournament after a monthlong layoff, and rustiness might explain her 41 unforced errors, including seven double-faults. And the 20-year-old Garcia kept Williams on her heels with deep groundstrokes and serves that topped out at 117 mph.

"I can play a hundred times better," Williams said. "I really gave myself a tremendous amount of trouble out there. Granted she played great, but I made so many errors ... 40-something errors. It's not the way to play professional tennis. Maybe amateur."

Three-time champion Novak Djokovic was off Saturday but advanced to the fourth round anyway when his next scheduled opponent, Florian Mayer, withdrew because of a groin injury. Djokovic's next match will be Tuesday.

Wawrinka rebounds

Stanislas Wawrinka bounced back from his first loss of the year by beating Daniel Gimeno-Traver 6-0, 3-6, 6-3. No. 7 Tomas Berdych joined Wawrinka in the third round by beating Stephane Robert 7-6 (5), 6-1.

No. 10-seeded John Isner rallied to win an all-American matchup against Donald Young, 6-7 (5), 6-3, 6-4. Isner is back in the top 10 this week for the first time in 18 months.

Sam Querrey, Ryan Harrison and Jack Sock lost second-round matches. That left Isner as the lone remaining American in the men's draw, reflecting the state of U.S. tennis.

Williams and Garcia engaged in a succession of side-to-side baseline exchanges that had the stadium crowd roaring. But she finished in a hurry, serving out the final game at love with the help of consecutive aces.

Reigning Wimbledon champion Andy Murray has predicted that Garcia will someday climb to No. 1, but the Frenchwoman is now 0-3 against Williams.

"It's always nice to play against a big player," Garcia said. "You are working and practicing to play this match, because it's in this kind of match you can learn more. But next time I prefer to win."

Williams is playing for the 14th time at Key Biscayne, an hour from her home in Palm Beach Gardens. She won the event for the first time in 2002 and tied Andre Agassi's record of six titles last year.

With files from The Associated Press