KEY BISCAYNE, Fla. (AP) — Novak Djokovic often bounces the ball more than a dozen times before serving, and the tedious ritual may have cost him a match Friday.

The defending champion at the Sony Ericsson Open went into a funk after being warned for taking too much time between points, then blew a third-set lead to lose his opening match.

Qualifier Kevin Anderson, a 6-foot-7 former NCAA doubles champion at Illinois, beat the third-ranked Djokovic 7-6 (1), 3-6, 6-4.

Djokovic won his first Grand Slam title at this year's Australian Open and was coming off a title at Indian Wells last week. But he struggled from the start against Anderson and was rattled by the warning from the chair umpire.

Serving at 2-0 in the third set, Djokovic won the next point after the warning to reach deuce, then lost 13 points in a row. Jeers from the crowd further agitated him, and by the time Djokovic collected himself, Anderson was up a break at 3-2.

"I didn't focus myself in that moment," Djokovic said. "But, you know, that's OK. It's all part of the game."

Anderson, a big-serving South African, played for three years at Illinois and won the 2006 NCAA doubles title. He turned pro last year, and the victory was his first over a top-10 player.

"I kept telling myself, 'I can do this. I've just got to believe in myself,"' said Anderson, ranked No. 122. "Even still, just knowing what he's done and what a great player he is, to have beaten him is a tremendous experience for me."

Another qualifier, Benjamin Becker, had no luck against second-seeded Rafael Nadal, who won 7-5, 6-2. No. 7 David Nalbandian lost to Xavier Malisse 6-1, 6-4, and No. 8 Richard Gasquet was beaten by Dmitry Tursunov 6-3, 6-7 (2), 7-6 (5). No. 9 James Blake eliminated Andreas Seppi 7-5, 6-3.

In women's play, defending champion Serena Williams, three-time champion Venus Williams and top-ranked Justine Henin won their opening matches in straight sets.

Serena, seeking her fifth Key Biscayne title, reached the third round by beating Edina Gallovits 6-1, 6-2. Her older sister double-faulted seven times but swept Marta Domachowska 6-4, 6-3. Henin defeated Angelique Kerber 6-4, 6-2.

Seeded players had opening-round byes and were in action for the first time Friday.