WIMBLEDON, England — Dinara Safina served balls long, dumped quite a few into the net and put several wide. She once even served to the wrong half of the court.

Despite her 15 double-faults, though, the top-ranked Russian reached the Wimbledon semifinals for the first time by beating unseeded German teenager Sabine Lisicki 6-7 (5), 6-4, 6-1 Tuesday.

"I was Santa Claus on the court, serving so many double-faults," said Safina, who will face five-time champion Venus Williams on Thursday in the semifinals.

Safina struggled with all aspects of her service game on a sunny Centre Court, from her toss to her execution to even her direction.

Trailing 5-3 in the first set, Safina was serving at 30-0. After a first serve that failed to land in, she double-faulted for the sixth time by sending her second serve into the far corner of the wrong service box.

"I start the serve, but I don't end up the shot. I'm going away," Safina said. "That's why I'm serving double-faults. I'm not finishing the serve. It's kind of technical."

On set point for Lisicki in the tiebreaker, Safina double-faulted for the seventh time and then smashed her racket into the grass, drawing a code violation from the chair umpire.

"Sometimes even I don't know what I'm doing with my serve," Safina said. "I think for the serve, it's not me there serving."

Safina also complained about several line calls, and when she successfully challenged a call that would have led to yet another double-fault in the final game of the second set, she gave the chair umpire a distasteful look and uttered a comment.

The Russian won another challenge in the sixth game of the final set, shortly after she double-faulted three straight times to allow Lisicki to get to deuce. Safina hit a forehand that landed on the baseline, but it was called out. She won the challenge and then took a 5-1 lead when Lisicki put a backhand into the net.

"I was tough mentally," Safina said. "That was the key today."

The 19-year-old Lisicki played well for some of the match, even serving 12 aces — 12 more than Safina could manage. But she called for a trainer because of a calf cramp after being broken for the third straight time in the third set.

The trainer massaged Lisicki's right calf, but she won only the three points from the double-faults in the next game.

"I just went out there to fight," Lisicki said. "I gave it all I had, but she was physically fitter than me today."

In their only other meeting, Lisicki beat Safina in the first round of the 2008 Australian Open.

"Back then was the first round. Now it's the second week," Lisicki said. "I think she just knew how to handle it physically better than me."

Safina will have another tough match against the third-seeded Williams, the two-time defending champion who easily beat 11th-seeded Agnieszka Radwanska of Poland 6-1, 6-2.

"If I play my best and she plays the best, it's 50-50 who's going to win the match," Safina said. "I don't think if I play my best tennis and she plays the best tennis that she's the favorite. I think I still have a chance."