Key Biscayne, Florida: Juan Martin del Potro's latest comeback from an injury is off to a slow start, and he's OK with that.
Playing his first match since Jan. 15, del Potro lost Thursday to Vasek Pospisil in the first round of the Miami Open, 6-4, 7-6 (7).
"I don't feel frustrated," del Potro said. "I have to take the positive things on my comeback. The score doesn't matter for now."
Del Potro had been sidelined with a lingering left wrist injury. The 2009 U.S. Open champion had wrist surgery a year ago and played in just four tournaments in 2014, and his ranking has fallen to No. 616.
Venus Williams began her 16th appearance at Key Biscayne by beating qualifier Urszula Radwanska 6-3, 6-2. Radwanska's sister Agnieszka won, as did former No. 1 Caroline Wozniacki.
Del Potro's rustiness showed in the second set, to the disappointment of a partisan stadium crowd rooting for the Argentine. He served at 5-4 and was broken. He double-faulted holding a set point, lost another set point and double-faulted again on the next-to-last point.
Del Potro converted only one of six break-point chances and hit just nine winners to 36 for Pospisil, a Canadian ranked 60th.
"I didn't serve well in the special moments," del Potro said. "But now I'm OK. Just playing the tournament and being here means a lot for me."
Del Potro said he felt fine physically after the match. He said his wrist is not yet 100 percent, but it's improving week by week.
"It doesn't matter how long it takes me to be at the top again," he said. "I just wanted to play tennis and without pain."
Williams, seeded 16th, lost serve three times and committed 21 unforced errors but still advanced in barely an hour. The typically windy weather on the island required an adjustment, she said.
"Those were really challenging conditions," she said. "The wind literally blew so many balls in that were going out."
Williams improved to 55-13 at Key Biscayne, where she won titles in 1998, 1999 and 2001.
"Been down here a little over forever," said Williams, who lives 90 minutes up I-95 in Palm Beach Gardens. "I love playing down here."
Aside from Williams, American women went 0-3, with Madison Brengle, Christina McHale and Varvara Lepchenko losing. Wozniacki, seeded No. 4, beat Brengle, 6-0, 6-1. No. 9 Andrea Petkovic swept McHale 6-2, 6-2. No. 28 Lepchenko was eliminated by Kaia Kanepi 6-2, 6-4.
No. 7 Agnieszka Radwanska defeated Anna Schmiedlova, 6-4, 7-5. Seeded players competed in their opening matches after receiving first-round byes.
On the men's side, American Steve Johnson lost to Mikhail Kukushkin, 6-4, 3-6, 6-2. Former Australian Open runnerup Marcos Baghdatis was eliminated by Simone Bolelli, 6-2, 6-2.
Martin Klizan won and will face No. 1 Novak Djokovic in the second round Saturday night.
Seven-time champion Serena Williams, Rafael Nadal and Andy Murray are among those playing their opening matches Friday.