KEY BISCAYNE, Fla. — Andy Roddick hit a shot not found in any how-to manual, and it came at a critical time to help him survive a scare today in his opening match at the Sony Ericsson Open.

The sixth-seeded Roddick beat qualifier Viktor Troicki 5-7, 6-2, 6-4.

With Troicki serving at 4-5 in the final game, Roddick's creativity helped him win the first point. A rally forced him to the sideline near the net, and when Troicki sliced a volley to the other side, Roddick chased down the ball as it bounced away from him, then spun to yank a backhand crosscourt past the Serbian.

The ball landed on the sideline, but Roddick wasn't sure the shot was good until the crowd erupted with a standing ovation.

"I didn't even see it," he said. "I heard people yell and scream afterward, and I figured that was a good thing. As far as freak show trick shots, that's up there. You don't hit shots like that every day."

Five points later Troicki pushed a backhand wide, and Roddick had his victory.

Top-ranked Roger Federer won with less drama. Still seeking his first title this year, he erased all seven break points he faced and beat Gael Monfils 6-3, 6-4.

"I played well on the big points," Federer said. "The times he had break points, many times I served well and stayed aggressive. All in all, I think I played a very good match."

Eight seeded men lost, including No. 5 David Ferrer, No. 13 Andy Murray and No. 21 Lleyton Hewitt. Ferrer, a two-time semifinalist, was beaten by Thomas Johansson 6-4, 7-5. Murray, a semifinalist last year, lost to Mario Ancic 6-2, 2-6, 7-6 (7). Hewitt was eliminated by Jose Acasuso 6-3, 7-6 (4).

On the women's side, Lindsay Davenport played at Key Biscayne for the first time in five years and needed only an hour to eliminate Camille Pin 6-2, 6-1. Second-seeded Ana Ivanovic beat Emelie Loit 6-1, 6-2 and advanced to a third-round match Sunday against Davenport.

It will be the first meeting between Ivanovic, 20, and Davenport, 31.

" I have to approach it as if it's a final," Ivanovic said. "Growing up I saw her winning in Grand Slams, and she's such a great player and great champion. So I expect a very tough match."

Roddick, off to his best start in three years, improved to 16-3 in 2008. He won despite struggling with his serve early, and survived a 20-point game at 1-1 in the final set, erasing five break points.

"To my credit, on a couple of break points we played long points and there were rallies, and I didn't play myself out of them by making an error," Roddick said. "I kind of stayed the course. After I got through that game, I felt like the match was mine to take."

Roddick fell behind early because he made only 35 percent of his first serves in the opening set.

"I normally have pretty high percentages on my first serve," he said. "It was just a technical adjustment. Maybe I was a little anxious to get out there, but the toss was out in front. I brought it back, and it clicked back in."

Davenport, seeded 32nd, lost just six service points in her successful return to Key Biscayne. Injuries, an aversion to the island's windy weather and a pregnancy last year kept her away.

"I would have never thought that five years ago would have been my last time I played here," she said. "But I have to say I've really enjoyed myself so far this year. I was excited when I got back out on that court. It's a great, great center court."

Davenport left the WTA Tour in late 2006 to have her first child. The three-time Grand Slam champion rejoined the tour last summer and is 16-3 this year, with two titles.

She needed only an hour to beat Pin.

"I was kind of trying to get used to the conditions out there," Davenport said. "For here it's a pretty calm day, but it's still a steady breeze going one way. But I was happy to get off the court relatively fast and pretty efficient."

No. 5 Anna Chakvetadze reached the third round by beating Tamira Paszek 6-3, 6-2. No. 7 Daniela Hantuchova and No. 10 Elena Dementieva also won. Seeded players had first-round byes.

No. 12 Nicole Vaidisova lost to qualifier Alisa Kleybanova 6-4, 6-0. No. 14 Nadia Petrova retired in the first set against Zheng Jie because of strained thigh.

In other men's play, Ivo Karlovic remained winless at Key Biscayne, even though he keeps coming close. The 19th-seeded Karlovic fell to Julien Benneteau, 3-6, 6-4, 7-6 (2).

Karlovic has played in the event the past five years, losing his opening match every time. He has gone to a third-set tiebreaker each of the past three years, and his latest defeat came despite 21 aces.

No. 14-seeded Tommy Robredo, No. 26 Philipp Kohlschreiber, No. 29 Fernando Verdasco and No. 30 Juan Ignacio Chela also lost.