Defending champion <a href="https://www.thenationalnews.com/tags/carlos-alcaraz/" target="_blank">Carlos Alcaraz</a> overcame a mid-match slump to reach the <a href="https://www.thenationalnews.com/tags/wimbledon/" target="_blank">Wimbledon </a>quarter-finals on Sunday, beating France's Ugo Humbert in four sets on Centre Court. The Spanish world No 3 came through 6-3, 6-4, 1-6, 7-5 against his 16th-ranked opponent to book a spot in the last-eight of a Grand Slam for the seventh time in a row and the ninth in just 14 appearances. However, it was another mixed afternoon for Alcaraz, who had needed five sets to see off the American Frances Tiafoe in the third round. His erratic performance on Sunday saw him drop serve five times and commit an uncharacteristic 33 unforced errors. The 21-year-old, seeking to become just the sixth man to win the French Open and Wimbledon back-to-back, eased through the first set under the Centre Court roof before crucially saving four break points in the fifth game of the second. A set he sealed in thrilling style having hit the deck mid-rally. Humbert stormed back, though, breaking the champion three times in the third set as Alcaraz went off the boil. Alcaraz was twice unable to hold on to breaks in the fourth set and had to fend off three break points in the eighth game to stay level at 4-4. Left-hander Humbert then lost his edge to hand over a service break in the 11th game and Alcaraz took full advantage to quickly seal the tie. Alcaraz will take on either American 12th seed Tommy Paul or 36-year-old compatriot Roberto Bautista Agut, a semi-finalist in 2019. "Playing lefties is always tricky, no matter the surface," said Alcaraz in his on-court interview after the match. "I played my first leftie at Queen's so I learnt a little bit from that. I felt great playing today, I think I played a really high level and playing a leftie I tried not to think about it and just played my own game." Asked about the stunning point which sealed the second set, he added:<b> </b>"Unbelievable, I guess! I just try to fight for every ball, it doesn't matter which part of the court I am, I just try to run in whichever part of the court I am on. Giving myself the chance to stay alive in the point. "Set point is a really important point for me so I had to show the opponent that whatever shot he shoots, I will be there. That's me, I will be there, fighting until the last ball and sometimes it is a good point like this one and sometimes I lose it but the main thing is just to fight. "I just choose the shot when I am going to hit it. I don't think about it beforehand. I like the forehand drop shot, passing shot from the forehand or the lob tweener, that is my favourite shot so I try to find that in every match." Meanwhile, top seed Jannik Sinner quelled the challenge of big-serving 14th seed Ben Shelton with a 6-2, 6-4, 7-6 victory that sent him into the last eight. Sinner, who could meet Alcaraz in the semi-final, will first have to get past fifth seed Daniil Medvedev or 10th seed Grigor Dimitrov in the quarters. In the women's draw, French Open runner-up Jasmine Paolini reached her first Wimbledon quarter-final when Madison Keys had to retire with a leg injury at 5-5 in the third set of their fourth-round match Sunday. Keys had served for the match at 5-2 in the last set but then started limping more and more and needed a medical timeout to get her left leg worked on after Paolini made it 5-4. She had her left thigh taped as she served for the match for a second time but was broken again — double-faulting on break point – and was in tears by the end of that game, with her movement clearly restricted. “I’m so sorry for her. To end the match like this, it’s bad,” Paolini said. “What can I say? We played a really good match. It was really tough. A lot of ups and downs. I’m feeling a little bit happy, but also sad for her. It’s not easy to win like that.” Paolini is the fifth Italian woman to reach the Wimbledon quarter-finals in the professional era, and will try to become the first to make the semi-finals. She will face the winner between Coco Gauff and Emma Navarro.