Not familiar territory for the four-time winner of The Championships.

“Yeah,’’ she said Monday afternoon, shortly after advancing to the quarterfinals by escaping Yaroslava Shvedova, 6-1, 2-6, 7-5. “I don’t talk about that.’’

Had it not been for her ability to recover from a second-set dip against the 24-year-old Russian-born Shvedova, Williams would have been left to detail another bitter loss on the heels of her recent defeat in the French Open. After easily dismissing Shvedova in the opening set, Williams, lumbering at times and unable to track down her more agile opponent’s deep returns, lost the second set on consecutive service breaks (Games 6, 8). In the eighth game, Williams jumped ahead, 30-0, only to hand over the set eight points later.

“Hard to get a read how she’s really feeling,’’ said John McEnroe, in his commentator’s role for the BBC, sounding somewhat miffed by the less-than-dominant Williams. “She’s trying to go down as the best female player ever . . . she’s not moving as well as I’ve seen her in the past.’’

After taking a year off because of injuries, Williams is back, but clearly not at her best. In peak form, the winner of 13 Grand Slam events typically could dropkick a newbie the likes of Shvedova over the filligree fence of the All England Club. She remains the most powerful woman on the tour, her strength game, especially her serve, her trademark and no doubt her legacy.

“The greatest serve in the history of the women’s game,’’ noted McEnroe.

Meanwhile, the sinewy, 5-foot-11-inch Shvedova was nearly Williams’s equal at the service game, although Williams held a decided edge (12-7) in aces and only had half the double faults (3-6). However, Williams averaged 104 miles per hour on her first serves, and Shvedova was 103. Williams dipped to 84 on second serves and Shvedova to 87. In other words, Shvedova was right there with her, in both shot and muscle, especially once shaking her doldrums midway through the second set with that first break for the 4-2 advantage.

In set No. 3, it took Williams until the 11th game to gain the winning foothold. Serving at 5-5, Shvedova first double-faulted to go down, 15-40, then lost the game when she fired a routine backhander wide right. Easy shot, but the worst result, leaving Williiams with the 6-5 lead. Six points later, it was over, Williams delivering a deep backhander down the left side that the hard-charging Shvedova couldn’t hunt down.

“I definitely felt like I let her back in the match,’’ said Williams, though lauding Shvedova’s efforts. “She’s a great player and she’s been doing really well.’’

As for her own game, Williams knows that still needs some burnishing.

“I felt like I was sluggish out there,’’ she said. “Just pulling myself together, mentally. I feel like I can do a lot better, which is very comforting — because if this is my best, I’m in trouble.’’

No backing down

His back an unexpected nuisance and his opponent much the same, Roger Federer once more turned his racket into his convenient painkiller, advancing to the quarterfinals with a 7-6 (7-1), 6-1, 4-6, 6-3 victory over Xavier Malisse on Centre Court.

Before it was over, both players took timeouts for medical aid (Federer for his back, Malisse for a knee), and both endured a rain delay that once again had tournament officials in angst over whether to close the court’s roof. It remained open for the match, which might not have been great for his back, said Federer, even though he prefers the open-air approach.

“It is an outdoor tournament, at the end of the day,’’ he said. “We don’t want to play indoors all the time. They do a great job here. They love it. To see the referee coming out and inspecting the courts, that’s the whole drama that belongs to Wimbledon.’’

Of much greater concern to Federer is his back, one that has caused the six-time Wimbledon champ only temporary issues over the years.

“Honestly,’’ he said, “I’m not too worried. I’ve had bad backs over the years. I’ve been around. They go as quick as they come. But of course I have to keep an eye on it. I am pretty convinced — otherwise I wouldn’t have been able to pull out the match the way I did.’’

Mob squad

Following her win on Court No. 2 (a.k.a. the Badlands for someone of her curriculum vitae), Williams needed extra time and the help of multiple security guards to make it back to the dressing room. Key issue: the crush of adoring fans. “I was totally mobbed,’’ Williams said. “Literally, I thought I was going to fall down after the match. I guess that comes with the territory. It was crazy out there.’’ . . . Kim Clijsters, who said long before Wimbledown that she will retire — for good this time — this year, fell to Angelique Kerber, 6-1, 6-1, a fairly unceremonious end on these courts. “I won’t be sorry about anything,’’ said Clijsters, caring not to dwell on her farewell. “Every time I’ve played here, I’ve given my best and that’s the only thing I can try. Some days it’s good. Some days it’s great. And some days it’s not good enough.’’ Kerber faces fellow German Sabine Lisicki, who rubbed out top-seeded Maria Sharapova . . . Defending champion Petra Kvitova, after stumbling out of the gate, nipped Francesca Schiavone, 4-6, 7-5, 6-1. Kvitova takes on Williams in the quarters, potentially the best of the women’s matches to be played here . . . It would not be a real Wimbledon without rain playing havoc with the schedule. By late afernoon and into the evening, the only ongoing match was under the Centre Court roof, with defending champ Novak Djokovic making easy work of Viktor Troicki. All other play was abandoned at 7:47 p.m.

Kevin Paul Dupont can be reached at dupont@globe.com. Follow him on Twitter @GlobeKPD.