India's seventh-seeded Sania Mirza suffered her sixth loss in seven matches, falling 7-5, 6-4 to Canada's Stephanie Dubois in her opening match at a $220,000 WTA hardcourt tournament.
Mirza, battling a left knee injury suffered three weeks ago in a first-round Wimbledon exit, reached the Charleston quarter-finals in April as a qualifier but has won only once since and struggled again in a match that dragged past midnight to finish in the early hours of Tuesday.
"I felt like I was really rusty," Mirza said. "I played OK a few games and then I didn't. It was just a matter of putting together a few games, which I couldn't do.
"But the good news is the knee doesn't hurt, so that's the positive I can take."
The 24-year-old walked onto the court only an hour before midnight after rain and lighting delays and battled for 95 minutes against a 117th-ranked rival she ousted in qualifying for this year's Australian Open.
"It's not easy with the weather and everything and playing in the middle of the night," Mirza said.
Mirza, whose only WTA title came in 2005 on home soil in Hyderabad, was also worried about how her knee would make the transition to hardcourts in her first tune-up event for the US Open.
"I was a bit concerned about the knee. Hardcourt is tougher on the knee," Mirza said. "As we go to the US Open and courts get faster, I hope I can do better."
Mirza, ranked 62nd, was long with a backhand and forehand to surrender a break in the final game of the first set, then sent a forehand long to drop her fourth game in a row and fall behind 2-0 in the second set.
But Mirza fought back, winning the next four games in a row, saving two break points in the sixth game for a 4-2 edge, only to drop the final four games.
Dubois advanced to a second-round match against Britain's Heather Watson, who ousted Greece's Eleni Daniilidou 6-4, 6-1.
British Women's No. 1 Elena Baltacha ousted Kazakhstan's Yaroslava Shvedova 6-2, 7-6 (7/5) to reach a second-round match against France's Virginie Razzano, who eliminated Japanese wild card Misaki Doi 6-2, 6-2.
"I haven't played Razzano in a long time," Baltacha said. "I know its going to be a tough match, but I'm definitely looking forward to the challenge."
Vavara Lepchenko was leading fellow American Sloane Stephens 4-3 when their match was halted by darkness as the main stadium lights failed to start on schedule at the first-time WTA venue.
After the illuminating pause, 101st-ranked Lepchenko outlasted wild card Stephens 4-6, 6-4, 6-3.
The rain forced postponement until Tuesday night of a first-round match between Australian fourth seed Jelena Dokic and China's Zhang Shuai.
Top seed Shahar Peer also begins play Tuesday. The 24th-ranked Israeli veteran, a first-round loser in her past four events, will face Japanese qualifier Ryoko Fuda.
Peer was one victory shy of cracking the top 10 in April but has dropped five matches in a row over the past two months and slid 13 spots in the rankings from a career high.