Defending champion Andy Roddick lost his opening match at the Nasdaq-100 Open when a sprained right wrist forced him to retire while trailing Fernando Verdasco of Spain 7-6 (9), 4-3 on Friday.
No. 2-seeded Roddick received treatment twice during the second set but struggled in the final games, especially with his second serve.
Meanwhile, fifth-seeded Carlos Moya saved three match points to advance, while women's second-round winners included defending champion Serena Williams, three-time Grand Slam champ Justine Henin-Hardenne, who played her first match in six months, three-time Key Biscayne champ Venus Williams, and second-seeded Maria Sharapova.
Roddick said his mild sprain occurred when he hit a forehand at 5-all in the first set against Verdasco.
"I just caught something the wrong way and jammed it a little bit," he said. "Right now they don't think there's anything long-term, but it's going to take some rest.''
Roddick said a trainer told him he risked further injury by continuing. When taping the wrist didn't help, he retired.
No. 12 Tommy Robredo beat veteran Jonas Bjorkman of Sweden 6-4, 6-0 and then withdrew, citing shoulder inflammation that has bothered him for six months. No. 24 Jiri Novak of the Czech Republic eliminated Kevin Kim 6-1, 6-2 and advanced to the fourth round because of Robredo's withdrawal.
Former French Open champion Juan Carlos Ferrero beat No. 11 Guillermo Canas of Argentina 6-4, 2-6, 6-4. Xavier Malisse, seeded 32nd, was defaulted for cursing a linesman while leading David Ferrer of Spain 6-3, 5-5.
Henin-Hardenne, sidelined since the US Open by a virus and knee injury, beat Abigail Spears of the US 6-4, 6-3.
"It feels very good," said Henin-Hardenne, seeded 19th. "It's still hard at the beginning to find the rhythm and everything. But just the fact that I'm back on the courts, it's great."
Third-seeded Serena Williams opened her bid for a fourth consecutive Key Biscayne title by beating Vera Douchevina 6-3, 6-0. Venus Williams took just 50 minutes to beat Anna-Lena Groenefeld of Germany 6-2, 6-0. Williams is seeded eighth and seeking her first tournament title since July.
Sharapova lost only eight points in the opening set and beat Eleni Daniilidou 6-0, 6-4.
Vera Zvonareva fell to Nuria Llagostera Vives 3-6, 6-3, 6-1 for the Spaniard's best career win. Also advancing were seventh-seeded Alicia Molik, No. 11 Patty Schnyder of Switzerland, No. 14 Francesca Schiavone of Italy, No. 15 Elena Likhovtseva of Russia, No. 21 Ai Sugiyama and fellow Japanese, No. 23 Shinobu Asagoe.