Defending champion Carlos Alcaraz cruised past Alexander Zverev to reach the Madrid Open quarter-finals but Daniil Medvedev fell to a shock defeat.

The 19-year-old Spaniard will face Karen Khachanov in the last eight after he beat fifth seed Andrey Rublev.

Medvedev, seeded second, complained about the crowd in a 7-6 (7-1) 6-4 loss to fellow Russian Aslan Karatsev.

The world number three returned to his chair because of booing from the crowd during the first-set tie-break before the chair umpire was able to encourage him to return to the court.

He also claimed there was a lack of space behind the baseline on Arantxa Sanchez Stadium as he was knocked out by his 121st-ranked compatriot.

US Open champion Alcaraz is bidding to win back-to-back titles following success in Barcelona two weeks ago, and leads the tour in clay court wins this season - with this his 16th.

The home favourite took just 83 minutes to dismiss Zverev, who continues to try to rediscover his form following a serious ankle injury sustained during last year's French Open.

"For me it's amazing to play the level that I played today," said Alcaraz, who has lost just twice in 28 matches in 2023.

"It has been a question mark for me. I played well, I feel really good and this match gives me a lot of confidence.

"I just want to enjoy playing here in the Caja Magica in front of my home crowd. It's been amazing for me so I just enjoy every moment."

Russian 10th seed Khachanov awaits Alcaraz after beating in-form compatriot Rublev 7-6 (10-8) 6-4.

In the women's draw, Belarusian second seed Aryna Sabalenka recovered from an early scare as she came back from a set down against unseeded Egyptian Mayar Sherifin to prevail 2-6 6-2 6-1 and secure her semi-final place.

Greek ninth seed Maria Sakkari meets Romanian Irina-Camelia Begu later, before world number one Iga Swiatek and third seed Jessica Pegula attempt to progress from their respective last-eight matches on Wednesday.