LONDON (AP) - Juan Martin del Potro faces some major challenges if he's going to go any further at Wimbledon after reaching consecutive Grand Slam quarterfinals for the first time since 2012.
First, on Wednesday he'll take to the court for a third consecutive day amid concerns over his fitness. Second, his opponent will be two-time Wimbledon champion Rafael Nadal.
2009 U.S. Open champion Del Potro defeated Gilles Simon 7-6 (1), 7-6 (5), 5-7, 7-6 (5) in a match that was carried over to Tuesday to complete the men's quarterfinal lineup at the All England Club.
The other matchups see defending champion Roger Federer against Kevin Anderson; Novak Djokovic takes on Kei Nishikori and Milos Raonic meets John Isner in a matchup of big servers.
After reaching the French Open semifinals last month, Del Potro - who has missed long periods with a career-threatening left wrist injury - returned to his career-high ranking of No. 4 for the first time since February 2014, which he acknowledges is a "good signal".
"I don't know if I'm better or not, a better player than few years ago," said Del Potro, after returning to the last eight at Wimbledon for the first time since 2013. "I'm doing a good season already. I'm very proud to be in the last eight players of this tournament"
Del Potro's Roland Garros run was ended by eventual champion Nadal. If the Argentine is to make it back-to-back last four appearances, he will need to reverse that result on Wednesday.
"If I want to beat him (Nadal)," Del Potro said. "I have to come to the net very often and play hard with my forehands, with my backhands, and try to take all the chances."
With the fifth-seeded Del Potro's fourth-round match - the longest men's singles contest of the tournament so far - having required to be finished Tuesday, he will be taking to the court for a third consecutive day.
Given the fact he withdrew from a pre-Wimbledon event with a groin concern and called the trainer during his match with Simon, Del Potro's fitness could be a factor.
There is little doubt that Nadal - who is playing in the Wimbledon quarterfinals for the first time since 2011 - will provide a big test.
• WOMEN'S RECAP: Serena Williams came up with a comeback to reach the semifinals at Wimbledon, then walked off Centre Court with her right index finger aloft.
Williams moved closer to her eighth title at the All England Club and 24th Grand Slam trophy overall - but first since missing more than a year while having a baby - by beating 52nd-ranked Camila Giorgi of Italy 3-6, 6-3, 6-4 in the quarterfinals.
Next up for the 36-year-old American is a match against No. 13 seed Julia Goerges of Germany, a 3-6, 7-5, 6-1 winner against No. 20 Kiki Bertens of the Netherlands.
The other semifinal Thursday will be No. 11 seed Angelique Kerber of Germany vs. No. 12 Jelena Ostapenko of Latvia. Kerber needed seven match points to close out No. 14 Daria Kasatkina of Russia 6-3, 7-5 at Centre Court, while Ostapenko defeated 2014 Australian Open runner-up Dominika Cibulkova of Slovakia 7-5, 6-4 on a windy No. 1 Court.