(Photo credit: John E. Sokolowski-Imagn Images)

Alexander Blockx of Belgium was the latest player to secure his first career top-10 victory when he upset Canadian third seed Felix Auger-Aliassime 7-6 (3), 6-3 on Monday in the third round of the Madrid Open.

Blockx, 21, reached the Round of 16 for the second straight ATP Masters 1000 event after first doing so at the Monte Carlo Masters.

His first career match against Auger-Aliassime, ranked fifth in the world, was by far the biggest achievement of his young career.

'In the first set, I was just trying to find my game,' Blockx said. 'On my service games it went pretty smoothly, (as it did) on his service games. I had a couple of chances. But in the second set, it was one of my best levels I have played here.'

Blockx shone on his service games, winning 35 of 42 first-serve points (83.3%) and 50 of his 66 service points in all (75.8%) while firing five aces.

'I was serving amazing from the beginning of the match,' Blockx said. 'I had so much confidence. I didn't even think about panicking or losing my serve. I was playing well in the rallies, too, so I knew even if I missed a few serves, I could play the rallies.'

Blockx is the latest in a strong young contingent to earn his first top-10 victory during this tournament, after Spanish teen Rafael Jodar knocked off Australian Alex de Minaur and Croatian qualifier Dino Prizmic defeated Ben Shelton in earlier rounds.

No. 2 seed Alexander Zverev of Germany had to fend off a late stand from France's Terence Atmane to win 6-3, 7-6 (2). Atmane trailed 5-2 in the second set but saved two match points en route to forcing the tiebreaker, where Zverev ultimately seized control.

A two-time Madrid champion (2018, 2021), Zverev has now reached the Round of 16 in all nine of his starts at the tournament.

Zverev's next opponent will be Czech up-and-comer Jakub Mensik, the 23rd seed, who took down Russian 13th seed Karen Khachanov 6-4, 7-6 (11). Khachanov saved two match points during the tiebreaker but Mensik staved off four of Khachanov's set-point opportunities before getting the job done.

No. 7 seed Daniil Medvedev of Russia eased past Norwegian qualifier Nicolai Budkov Kjaer 6-3, 6-2 in 69 minutes, while No. 10 Flavio Cobolli of Italy won by the same scoreline over Paraguayan qualifier Adolfo Daniel Vallejo. Medvedev and Cobolli will meet in the fourth round.

Tour veteran Stefanos Tsitsipas of Greece was pleased with his performance in a 6-4, 6-2 win over Spanish qualifier Daniel Merida in 68 minutes.

'I really love the game when I get to discover tennis in such ways. Just hitting winners, missing a few times, but overall trying to take the most out of it. Seeing good rotation of my ball and seeing I can actually press and create some big shots, these are the types of moments that make me really enjoy the game,' Tsitsipas said.

His next opponent will be No. 12 Casper Ruud of Norway, who beat No. 20 Alejandro Davidovich Fokina of Spain 6-3, 6-1.

No. 16 Francisco Cerundolo of Argentina sailed past No. 18 Luciano Darderi of Italy 6-2, 6-3, and will take on Blockx in the Round of 16.

--Field Level Media