KEY BISCAYNE, Fla. -- 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 and 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 but 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.
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.
Djokovic, leading 2-0 but facing break point, was dribbling before a serve when umpire Norm Chryst warned him for taking too much time. Djokovic whacked a forehand winner to end that point and then screamed in the umpire's direction and shook both fists. The crowd hooted at the Serb.
Two points later, when Djokovic hit a first serve into the net, several fans cheered. He glared toward the stands and then lost the point and the game when he blew an easy volley.
Djokovic said he broke a shoelace during that rally.
"Obviously, the time violation and a lot of different things affected my service game," he said.
He rapidly unraveled from there, losing the next two games at love. Once Anderson took the lead in the final set, he kept it by serving well down the stretch, and on match point Djokovic slammed a forehand into the net.
Djokovic said he battled nerves at important moments against Anderson.
"Maybe I went for some shots too much, and he was wisely waiting for my mistakes," Djokovic said. "That was a crucial point."
Djokovic said he also felt a little tired. He's 17-4 this year as he heads to clay -- not his best surface.
"The good thing about this loss is that I can get a bit longer period of preparation and vacation as well," he said.
Serena Williams made herself right at home, as usual. Williams, who lives 90 minutes up Interstate 95 in Palm Beach Gardens, improved to 24-1 at Key Biscayne since 2002.
"I love playing here, I love having all my friends come and see me play," Williams said. "It's like playing at home. So I think any time you play at home, like the Patriots playing at home, you always have the extra oomph."
Henin showed no signs of the knee injury that troubled her at the start of the year. The Belgian hit 40 winners to only eight for her 80th-ranked opponent in raising her record this year to 13-2.
Henin began the year with pain in her right knee and considered surgery before deciding to treat the injury with cortisone and rest.
"I feel much better physically today than I did a few weeks ago -- that's for sure," Henin said. "So we could see it in my serve. ... I can play with my forehand again, and I feel that everything is better now."