KEY BISCAYNE, Fla. (AP)—Novak Djokovic’s mistakes mounted, and so did the fans’ frustration. Midway through the final set, when the Serb sent yet another unsightly shot wide, there was a collective groan and a smattering of boos.

A short time later, when Djokovic walked off the court defeated, the jeers were louder. He made a thumbs-up gesture in response.

With a listless, sloppy performance, the No. 2-ranked Djokovic lost his opening match Friday at the Sony Ericsson Open to Olivier Rochus 6-2, 6-7 (7), 6-4.

“I don’t feel great on the court, and everybody could see that,” Djokovic said. “Life goes on, you know.”

No. 4-seeded Rafael Nadal followed Djokovic into the stadium but not to the sideline, beating American Taylor Dent 6-4, 6-3.

On another dismal day for U.S. men, James Blake and Sam Querrey squandered one-set leads and were eliminated. In women’s play, former No. 1 Justine Henin, No. 2-seeded Caroline Wozniacki, No. 14-seeded Kim Clijsters and defending champion Victoria Azarenka advanced to the third round.

Henin beat No. 5 Elena Dementieva 6-3, 6-2.

Djokovic won the tournament in 2007 and arrived at Key Biscayne 15-3 this year and ranked No. 2. But he rarely hit aggressively against the 5-foot-6 Rochus, who lured Djokovic into a succession of long, grinding rallies.

“I wasn’t attacking,” Djokovic said. “I was just kind of waiting for him to make the shots, and it wasn’t the right approach. He was making me run a lot, so points were really long. That was exhausting.”

On a humid afternoon, Djokovic looked weary after only a few games. He double-faulted 10 times and lost 30 of 44 second-serve points, including 13 of 17 in the final set. He committed 62 unforced errors and converted only three of 13 break-point chances.

Rarely reaching 120 mph with his serve, Djokovic was broken three times in the final set, including in the last game.

“I was trying,” Djokovic said. “He was the better player.”

Rochus, ranked 59th, improved to 5-8 this year. It was the first time since 2002 he has beaten a player ranked so high, and the 29-year-old Belgian said his experience helped in the final set.

“In a match like this before, when I was younger, I would have never won,” he said. “I would have been mentally more negative.”

Blake watched much of the match and raved afterward about the 143-pound Rochus.

“The guy has so much talent,” Blake said. “I was saying to some of the people in the locker room, pound for pound, he’s got to be one of the best athletes in the world. Every ball it seems is over his head, and he’s getting up there and hitting it with such great strength and so cleanly.”

Wozniacki rallied past qualifier Tsvetana Pironkova 3-6, 6-3, 6-4, and Clijsters beat Petra Kvitova 6-1, 6-1. Azarenka beat Alexandra Dulgheru 6-3, 6-2, finishing shortly before rain began to fall, causing a 2 1/2 -hour delay.

There was another delay of 50 minutes later in the afternoon.

In other men’s play, No. 11-seeded Ivan Ljubicic retired with a back injury leading Benjamin Becker 6-4, 1-0. Ljubicic earned his first ATP Masters 1000 title Sunday at Indian Wells.

No. 24 Ivo Karlovic hit 28 aces, held every service game and beat Daniel Gimeno-Traver 6-3, 6-7 (5), 6-3. Karlovic had been 0-6 previously at Key Biscayne.

No. 12 Juan Carlos Ferrero and No. 15 David Ferrer also won.

Querrey, seeded 21st, was beaten by Jeremy Chardy 4-6, 6-4, 6-2. Blake lost to No. 27 Thomaz Bellucci 3-6, 6-1, 6-2.