Defending champion Carlos Alcaraz breezed into the third round at the US Open with another straight-sets win.

This time the victim was Lloyd Harris, who used to train with Alcaraz when the world number one was 15 at the Juan Carlos Ferrero Academy.

The South African gave Alcaraz a test in the third set but the seemingly unstoppable force still registered a 6-3 6-1 7-6 (4) win.

“I think I played a great match from the beginning until the last ball, but if I have to take something from the match I want to keep the level of the second set,” said Alcaraz, 20.

“I had to stay focused, stay strong mentally. It was pretty good for me and to win in straight sets is really important in the first rounds.”

There was a routine win for sixth seed Jannik Sinner, who beat fellow Italian Lorenzo Sonego 6-4 6-2 6-4.

American ninth seed Taylor Fritz also won in straight sets, coasting past Juan Pablo Varillas of Peru 6-1 6-2 6-2.

Alexander Zverev, seeded 12, won the all-German clash against Daniel Altmaier in four sets and will meet Grigor Dimitrov, the 19th seed who knocked out former champion Andy Murray.

Big-serving American John Isner called time on his career, fittingly enough, in a fifth-set tie-break as he lost his final match to compatriot Michael Mmoh.