WIMBLEDON, England -- Everything about Serena Williams' game is big: her forehand, her backhand -- and, especially, the searing serve.
But on the rare occasions when her powerful, slashing strokes are matched, she has a fail-safe device that sustains her through periods of vulnerability. It's something she rarely gets credit for, but is an essential part of what makes her the greatest women's champion of her generation.
It's called defense.
With Petra Kvitova, a fearless 20-year-old from the Czech Republic, crowding the baseline and taking some outrageous cuts at the ball, Serena fell back and operated in scrambling mode, chipping off-balance backhands and blooping forehands. She survived and advanced to a first-set tiebreaker, when her serve finally came alive.
In the end, Serena prevailed 7-6 (5), 6-2 to advance to Saturday's final, where she will face Vera Zvonareva. In the first semifinal, Zvonareva dropped the first set but rallied to defeat Tsvetana Pironkova 3-6, 6-3, 6-2. Serena has beaten Zvonareva five of six times in their head-to-head matches.
"It definitely wasn't easy," Serena said afterward. "I didn't expect to get this far after I played in the beginning of the tournament. I just felt off."
However, Serena's serve this fortnight has been historically huge. And though her ace and speed numbers were down Thursday -- there was talk that her right shoulder (taped in Wednesday's doubles match) was bothering her -- her serve constantly bailed her out. For the record, she had seven aces against Kvitova, and her six-match total (80) has already exceeded the Wimbledon record she set last year.
Ultimately, this match was about experience. Serena has fashioned a grass-court record of 58-7. Kvitova, an unorthodox lefty, is 5-5.
Zvonareva, meanwhile, was a prohibitive favorite in her match against the No. 82-ranked player in the world, but it was Pironkova who came out more aggressively. Gradually, that reservoir of confidence leaked away -- you could see it at the end of the first set when she needed a third set point to take the early lead -- and Zvonareva became bolder.
Nearly 10 years into her professional career and in her 30th major, Zvonareva is a finalist in a Grand Slam singles event for the first time. At 25, she is playing with a newfound calm. Maybe it's because tennis is only part of her life; she is pursuing a degree in international economic relations at the Ministry of Foreign Affairs in her hometown of Moscow.
Zvonareva has advanced one step beyond her 2009 run to the Australian Open semifinals, where she lost in straight sets to Dinara Safina. She has always had the physical talent to run deep into majors, but her head always held her back.
After sending home Jelena Jankovic and Kim Clijsters and now Pironkova, Zvonareva is playing freely and with unnerving poise. When she lost the first set, she said she had positive thoughts, not negative ones.
Pironkova, a 22-year-old Bulgarian who had never won even four matches in a row at the WTA level before the tournament, finally seemed to realize where she was: Wimbledon's Centre Court, the greatest stage in tennis.
Ultimately, Zvonareva's aggressive game carried her; she had 31 winners and converted 29 of 35 points when she journeyed to the net. She'll have to stay in that attacking mode against Serena.
"I will have to stay aggressive no matter what and not to let her dominate," Zvonareva said. "Because when Serena dominates, she's very difficult to play. I will try to fight for every point, and I think try to make it difficult for her on every point."
For Serena, the Wimbledon final is like an old, favorite sweater.
Ten of the past 11 Wimbledon finals have featured at least one Williams sister; four of them have seen Serena and Venus play each other. Serena, seeking her fourth Wimbledon title and 13th Grand Slam singles championship, will be a prohibitive favorite against Zvonareva. She has yet to drop a set in singles play here this year -- and, well, she's Serena Williams.
At age 28 -- the same as Roger Federer -- she is still in a major groove; a victory over Zvonareva would give her five Grand Slam singles titles in the past eight, going back to the 2008 U.S. Open. Three other players -- Svetlana Kuznetsova, Clijsters and Francesca Schiavone -- are all next in line, with one apiece.
"Vera's a great player," Serena said. "I've had some unbelievable matches with her. I feel like I have nothing to lose going into this match, but neither does she."
Greg Garber is a senior writer for ESPN.com.