LONDON — About an hour after flopping on her back and kicking her feet overhead to celebrate a stunning comeback against defending Wimbledon champion Petra Kvitova, Jelena Jankovic still was giddy.

“I cannot stop smiling. … I was very brave at the end. You know, here I am,” she said through a giggle. “Unbelievable.”

Jankovic kept using that word — “unbelievable” — as if trying to convince herself it were true that, despite never having much success on grass courts, she had put together a 3-6, 7-5, 6-4 victory Saturday over the No. 2-seeded Kvitova, who claimed the 2011 and 2014 titles at the All England Club.

“I was a little bit better at the end,” the 28th-seeded Jankovic said. “I was a little bit lucky, as well.”

The 30-year-old Serbian didn’t come out of nowhere: She was the runner-up at the 2008 U.S. Open and finished that season ranked No. 1. But she has never been past the fourth round at Wimbledon, hadn’t even made it that far since 2010, and won only one of five matches at the grass-court major over the last four years.

Kvitova, who led 4-2 in the second set, had a difficult time processing the match, too.

“I’m not really sure what happened out there,” she said. “Suddenly, I was just missing (shots). So it was really unusual, probably, or weird. I can’t really explain.”

After the traditional middle Sunday off, play resumes Monday. The top half of the women’s draw includes the most noteworthy matchup: Serena Williams vs. Venus Williams, meeting at a major for the first time since 2009. Those two, Maria Sharapova and Victoria Azarenka give that side of the bracket 34 Grand Slam titles.

And the eight women on the other half? They own zero major championships. That includes Jankovic, who meets No. 13 Agnieszka Radwanska next. Also Monday: No. 5 Caroline Wozniacki vs. No. 20 Garbine Muguruza, No. 15 Timea Bacsinszky vs. Monica Niculescu, and No. 21 Madison Keys vs. Olga Govortsova.

The men’s bottom-half matchups, which were determined Saturday: seven-time champion Roger Federer against No. 20 Roberto Bautista Agut, 2013 champion Andy Murray against No. 23 Ivo Karlovic, No. 22 Viktor Troicki against Vasek Pospisil, and 2010 runner-up Tomas Berdych against No. 12 Gilles Simon, who beat fellow Frenchman No. 18 Gael Monfils in a match that was moved under the roof at Centre Court as darkness arrived.

Troicki ended the run of Dustin Brown, the qualifier from Germany who stunned Rafael Nadal in the second round. It marks the fourth year in a row that a man ranked No. 100 or worse beat Nadal at Wimbledon, then failed to advance further.

To the locals’ delight, Murray beat No. 25 Andreas Seppi of Italy 6-2, 6-2, 1-6, 6-1. Early in the third set, Seppi got a visit from a trainer for his lower right leg, and ended up taking six games in a row. Murray received turnabout-is-fair-play treatment for a stiff right shoulder after falling behind 1-0 in the fourth set, and then took the last six games.

Kvitova lost three games through two matches, even apologizing to her parents for winning her opener in 35 minutes after they traveled from the Czech Republic to watch. But Kvitova ran out of steam against Jankovic, collecting only four winners in the final set after accumulating 20 before it.

“Not to be in the second week of (my) favorite tournament … is really sad,” Kvitova said. “I don’t really know what I can say.”

Jankovic, a real character, is rarely at a loss for words.

“I’m not old. I’m still young at heart,” she said at her news conference. “I look pretty good, so why not?”

Jankovic also delighted in discussing her suddenly, and surprisingly, effective serve.

“Maybe my serve is not as fast as some of those big girls. But if I’m hitting my spots, it’s quite effective,” Jankovic said. “It was … hard for Petra to attack and get some returns on it.”

Jankovic won 71 percent of her service points, matched Kvitova’s top speed of 109 mph (176 kph), and even wound up with 27 unreturned serves, including three aces.

That brought Jankovic’s ace total for the week to 28, tied with Serena Williams and others for second-most in the tournament, behind only Keys’ 42.

When that statistic was pointed out, Jankovic responded: “Is that for real?”

And with that, she chuckled as she leaned forward, covering her face with her left hand.