WIMBLEDON, England -- She's 30 now, the age when the body usually responds but the nerves can sometimes induce paralysis.
Since returning to tennis a year ago after some serious health scares, Serena Williams has been something less than the dominant champion who leads all active players with 13 Grand Slam singles titles.
After winning two of three majors to start 2010, Williams missed three straight. Her comeback at Wimbledon was a marginal success; she got to the fourth round, but lost to Marion Bartoli. The U.S. Open was better, but she fell easily to Samantha Stosur in the final.
Fine, Serena's fans reasoned, a good offseason will set her straight.
But it hasn't happened. She lost in the fourth round at the Australian Open and -- shockingly -- in the first round of the French Open to Virginie Razzano, of all people. Williams, who led by a set and 5-1 in the second-set tiebreaker, produced a monumental collapse. Once the living, breathing definition of swagger, Serena was tentative and, well, mortal.
It may be a terminal condition.
On Saturday, she came within an eyelash of losing her third-round match to Zheng Jie of China. Playing on the hallowed Centre Court, where Rafael Nadal met his doom and, on Friday, Roger Federer very nearly followed, Williams was forced to serve to stay in the match three times.
Finally, after 2 hours, 28 minutes, Williams was a 6-7 (5), 6-2, 9-7 winner. Afterward, she jumped up and down with joy after beating the WTA's No. 27-ranked player.
"Sometimes you just have to escape," said 1999 Wimbledon champion Lindsay Davenport, who called the match for the BBC. "Sometimes you need to win a match when you don't play exceptionally well.
"Zheng Jie might have played the best match of her life -- she just couldn't break Serena's serve. I'm impressed with how well Serena played with her back against the wall, how confidently she served."
Indeed, while the rest of her game -- particularly her movement, backhand and service return -- was idling along in C-minus mode, Williams' serve was sizzling. She produced 23 aces -- a Wimbledon record for a woman -- compared to just one for the outmanned Zheng, and saved all six break points. She won 80 of 98 points, an extraordinary percentage of 81.6.
"Geez," Serena said when told about the record. "It's good to know I can rely on that."
Zheng is listed at just over 5-foot-4, which doesn't help her on the high-hopping balls produced on clay and hard courts. But on grass, where the ball skids low, she is in a position -- especially when she crouches even lower to get a better look -- to hit the ball comfortably. She came into the match with a 12-6 record at Wimbledon, her best among the Grand Slams. Her best run in a major came here four years ago, when she reached the semifinals -- only to lose to Serena Williams.
There were more than a few moments when it looked like this match would be a fine piece of revenge symmetry for the 28-year-old. Zheng's serve is hardly daunting, but it baffled Williams long enough to cost her the first-set tiebreaker.
After the predictable second-set rebound, Williams settled into another nasty back-and-forth battle in the third. With Zheng serving at 7-all, Serena forced her to deuce twice. When a Zheng forehand glanced wide, Serena loosed a primal scream that could appropriately caption the famous, ubiquitous Edvard Munch painting.
Sister Venus, her partner in a doubles match later in the day, was in the players' box, along with parents Richard Williams and Oracene Price and, among others, actor Dustin Hoffman. For years, these early-round matches were automatic. Now, based on their anxious expressions, it appears they extract a heavy emotional toll.
In a postmatch news conference, Serena said that Zheng played "unbelievable on grass."
When the compliment was relayed, it brought a smile to Zheng's face.
"Yeah," she said, "After we finish the match, she just told me, 'You are crazy. You are crazy.'
"I just wish she can win this year."
This is the remarkably difficult road facing Williams if she wants to collect her fifth Wimbledon title:
On Monday, she meets unseeded Yaroslava Shvedova, who spanked Roland Garros finalist Sara Errani in straight sets. Shvedova is playing perilously well; she produced a golden set against the Italian, winning all 24 points of the first frame -- only the second time that has ever happened in the more than four decades of the Open era.
Is Williams scared?
"Um, no," she said, trying hard to be polite. "She's a really good player. She's such a solid player. I look forward to it. Hopefully I'll win a point in the set. That will be my first goal, and I'll go from there."
Presuming a victory (hardly a given), Williams likely will face defending champion Petra Kvitova in the quarterfinals, recent world No. 1 Victoria Azarenka potentially in the semifinals and No. 1-ranked Maria Sharapova in the final. That's a brutal ask.
"I was definitely much more calm than I was in my last long match that I lost [to Razzano]," she said. "I said to myself, 'Serena, stay calm.' I never thought I was going to lose the match.
"It was definitely a gut check. I've always been mentally strong, and that's not going anywhere."