WIMBLEDON, England -- French Open champion Li Na squandered two match points and lost 3-6, 6-4, 8-6 Thursday to wild card Sabine Lisicki in the second round of Wimbledon, the biggest upset of the tournament so far.

The 62nd-ranked Lisicki erased both match points with service winners in the ninth game of the third set and beat the third-seeded Chinese player under the roof on Centre Court.

After Li hit a forehand long on Lisicki's third match point, the 21-year-old German fell to her knees at the baseline and put her head to the turf. She broke into tears at her courtside chair.

"My emotions are so, I mean, just over the moon," said Lisicki, who served 17 aces and had 32 winners. "It's just amazing."

Li was up 4-2 in the third set and twice served for the match but was broken each time. She had won 14 of her previous 15 Grand Slam matches in 2011, reaching the final at the Australian Open, then becoming China's first major singles champion at Roland Garros last month.

Lisicki has won 12 of her last 13 matches on grass, including reaching the Wimbledon quarterfinals in 2009 and winning a tuneup tournament in Birmingham this month. She missed five months last season with a left ankle injury, and she fell out of the top 200 in the rankings.

"It was very, very hard," she said. "I really had to start from zero after being on crutches for seven weeks. So it just means so much to me, you know, winning the title in Birmingham and getting the wild card here. I appreciate it so much, to be back in Wimbledon. It's just a place that I love so much."

At 5-3 down in the third, Lisicki fell behind 15-40 on her serve and faced two match points. She came up with two service winners at more than 120 mph and two straight aces -- including a 124 mph delivery, the fastest by any woman at Wimbledon this week.

Li served for the match at 5-4 and 6-5 but couldn't convert.

"I just wanted to enjoy myself here and that's what I'm doing," Lisicki said. "That's what I told myself on the third set when I was down a break and she was serving for the match. I was just fighting and I wanted to stay longer out there.

"The crowd was cheering. I didn't know it could get so loud in there. It was just amazing. I loved it out there. The support was just amazing."

Earlier, defending champion Serena Williams recovered from a poor start to defeat Simona Halep 3-6, 6-2, 6-1 and move into the third round, staying on course for a fifth title.

After dropping the first set, Williams regained her renowned intensity and powerful shot-making to dominate the rest of the way on Court 2. The winner of 13 Grand Slam singles titles is still searching for her form after a yearlong absence because of injuries and health issues.

There were no tears this time from Williams, who sobbed with relief on Monday after winning her opening match on Centre Court against Aravane Rezai.

"I'm just happy to be playing and hopefully I'll get better as the tournament goes on," Williams said. "It was a little windy out there and I just was a little tight so I just got to relax and enjoy myself more."

Williams wasn't happy about playing out on Court 2, rather than Centre Court or Court 1. Her sister, five-time champion Venus, played her first-round match on Court 2. Their two other matches were on Centre Court.

"They like to put us on Court 2, me and Venus, for whatever reason," Serena said when asked about it in the press conference. "I haven't figured it out yet. Maybe one day we'll figure it out. I don't know."

Williams said top male players, such as Roger Federer, Rafael Nadal and Novak Djokovic, are "never moved across" to the outside court.

The Williams sisters have combined to win nine of the last 11 Wimbledon singles championships, including Serena's titles in 2009 and 2010.

"Actually Venus and I have won more Wimbledons together than a lot of the players or by ourselves in doubles even," she said. "At the end of the day, I don't know.

"They're not going to change, doesn't look like," Williams said, referring to All England Club organizers.

Told of Williams' comments, tournament spokesman Johnny Perkins said there was no intentional snub.

"I don't think it's anything deliberate, clearly," he told The Associated Press. "It's a hugely complex jigsaw puzzle. Everyone probably looks at it from their own point of view, so she's obviously quite entitled to (her opinion). ... We obviously have a duty to the paying public, plus the international audiences around the world."

From 4-2 in the second set, the seventh-seeded Williams won eight out of the last nine games to re-establish her supremacy on the grass at the All England Club, pumping a clenched fist and shouting "Come on!" after smacking key winners.

It was the fourth consecutive three-setter Williams has played since returning last week at the Eastbourne grass-court tournament. She had been out for nearly a year after two foot operations and blood clots in her lungs.

"I guess I just want to play longer matches because I can get more practice," she said.

In men's play, second-seeded Novak Djokovic swept into the third round by beating South Africa's Kevin Anderson 6-3, 6-4, 6-2 on Court 1. The Serb has won his opening two rounds in straight sets after his 43-match winning streak was ended by Roger Federer in the French Open semifinals.

"On the important moments, I served well, I played well and I returned really, really well today," said Djokovic, who has twice reached the semifinals at Wimbledon and will take over the No. 1 ranking if he makes the final this year. "In the first week, you have to stay focused. You're playing lower-ranked players with nothing to lose. It's just great to win two straight-set matches."

In a dramatic five-setter that lasted nearly four hours, No. 5 Robin Soderling came from two sets down to overcome 2002 champion Lleyton Hewitt 6-7 (5), 3-6, 7-5, 6-4, 6-4 in a second-round match played under the Centre Court roof.

The big-swinging Soderling, a two-time French Open finalist, broke Hewitt at love in the final game and dropped to his knees in exhilaration after the Australian slapped a forehand into the net on match point.

The 30-year-old Hewitt, whose career has been dogged by injuries, went up a break at 2-1 in the decisive set but couldn't hold on against the Swede.

Soderling withstood a bravura performance from Hewitt, who made at least three diving backhands during the match, two at the net and one running pass in the first set in which he rolled over after flicking the ball down the line to break serve.

"A player like Hewitt is not easy and I really showed I can play well against a good player on the big courts and turn around matches like this," Soderling said. "We had many matches in the past and I think this was the best we ever played."

A day after throwing his shoes in frustration, 2009 U.S. Open champion Juan Martin del Potro won 18 of 23 games Thursday to reach the third round with a 6-7 (7), 6-1, 6-0, 6-4 win over Olivier Rochus. At 6-foot-6, Del Potro stood about a foot taller than his Belgian opponent.