Kim Clijsters admitted she has surprised even herself at her last Wimbledon by reaching the fourth round.
She got the better of an ailing Vera Zvonareva. The Belgian was leading 6-3 4-3 when her opponent, who was struggling with breathing problems, decided she could no longer continue.
Clijsters plays German eighth seed Angelique Kerber next, on Monday if weather permits it, as she bids to reach the quarter-finals at the All England Club for a fifth time.
The 29-year-old, yet to reach the Wimbledon final, said: "I'm excited that I made it into the second week. A week ago I don't think I was expecting that, so I'm very happy with the way things have been going."
A stomach muscle problem sustained last week impeded Clijsters on the eve of Wimbledon.
"I have a couple days off now," she said. "I'm looking forward to it. There's such a special vibe whenever you get to the second week of a grand slam. I think here at Wimbledon, even more so. It just feels very unique."
Clijsters will retire for a second time after the US Open later this summer, when she will be seeking her fourth title in New York, but for now she is concentrating on making the most of the opportunities she has left.
She said: "Last year I was like, 'A year and a half to go. Oh, that long.' But now, as it's getting closer, I'm just really focused on what I have to do.
"Until after the Olympics, I don't think I'm going to be thinking about quitting or ending my career.
"The US Open will be a special occasion for me to be playing there and to end my career there. But it's something that I don't think about because it's not there yet. I'm sure it will be emotional."
Both players found the windy conditions on Court One tricky to handle but Clijsters was always the more consistent and, after winning the opening three games, she held on to win the first set.
Zvonareva took a lengthy medical time-out after three games of the second set and, when Clijsters broke to lead 4-3, the Russian called it a day.
Zvonareva is the last player to have beaten Clijsters at Wimbledon, in the quarter-finals in 2010, before going on to reach her second grand slam final, which she lost to Serena Williams.
Clijsters missed last year's tournament with a foot problem and injuries have continued to dog her, most recently the stomach problem, a recurrence of an injury which ended her season in August last year.
It remains a concern for the 29-year-old.
She said: "It's stable. It hasn't got worse in my second and third match, so that's obviously what I'm very happy about."
Kerber's rise has been one of the stories of the last 12 months, the 24-year-old climbing from outside the top 100 to break into the top 10.
Clijsters said of the match: "I've never played against her. It will be a first. Obviously playing a left-hander is always tough. She's been playing some really good tennis."
Despite her problems, Zvonareva was able to take to the court for her mixed doubles match with Marcelo Melo, the pair beating Juan Sebastian Cabal and Vera Dushevina.
The Russian insisted she had no choice but to pull out of the singles, though, saying: "It was not possible for me to play. You never want to retire during a grand slam, one of the great matches when you are playing a good player."
