Daniil Medvedev's new-found love affair with Parisian clay continued as he eased into the fourth round of the French Open.

The world number two had not won a match at Roland Garros prior to this year but has dropped just one set in three contests, with his latest success a 6-4 6-2 6-4 victory over giant American Reilly Opelka.

The 23-year-old is even taller than John Isner and enjoys playing on clay but this was Medvedev's day, the Russian breaking Opelka's serve five times to move into the last 16.

"Clay in Roland Garros feels great this year," said the 25-year-old. "Especially Wilson balls. I said it from the beginning. I think it's going to stay until the end of the tournament.

"Now I know to beat me, guys have to play good. This is always possible. It's better to feel like this than when you know you can lose to yourself just playing bad.

"I'm definitely happy with my game and my return today because I actually hit more aces than him. That's a great achievement."

Medvedev's fondness for the red stuff is likely to be tested in the next match when he takes on a clay-court specialist for the first time in Chile's Cristian Garin, who defeated Marcos Giron 6-1 5-7 6-2 6-2.

Sixth seed Alexander Zverev began his tournament by coming from two sets down to beat Oscar Otte but has been rock solid since and saw off Laslo Djere 6-2 7-5 6-2 to reach round four.

There he will play Kei Nishikori, who had won the first set against Henri Laaksonen 7-5 when the Swiss player retired through injury.

An amazing match on court 14 saw Spain's Alejandro Davidovich Fokina see off 15th seed Casper Ruud 7-6 (3) 2-6 7-6 (6) 0-6 7-5 after four hours and 35 minutes.

Ruud had reached at least the semi-finals of his previous four tournaments and was tipped as a dark horse but it was Davidovich Fokina who came out on top, saving a break point in the final game with an underarm serve.

Argentina's Federico Delbonis is another man having a great clay-court season and he reached the fourth round of a grand slam for the first time with a comprehensive 6-4 6-1 6-3 win against 27th seed Fabio Fognini.

The Italian, never one to hide his emotions, needed medical treatment after punching the strings of his racket in frustration.

There were four American men through to the last 32 for the first time since 1996 but Steve Johnson was the third to fall, going down 6-4 6-4 6-2 to 12th seed Pablo Carreno Busta.