US Open champion Daniil Medvedev reached the fourth round at Indian Wells with a 6-2 7-6 (7-1) victory over Serbia's Filip Krajinovic on Monday and says he is pleased to reach 50 wins this season.

The top-seeded Russian took to the court following a long rain delay in the Masters 1000 event and wasted no time in showing the kind of form that earned him a maiden grand slam title last month, going 4-0 up before taking the opening set.

Krajinovic fought back in the second set to lead 4-2 before Medvedev found his groove to force a tie-break, which he dominated to claim the win.

"I feel like I'm trying to play a little bit less ... just playing the biggest tournaments, or the ones that will get me back into shape," Medvedev said.

"So I'm really happy that I managed to get 50 (wins). It means I was doing pretty good in a lot of them.

"Filip is a really tough opponent. He's always playing top tennis, tough matches, especially that second set. There were a lot of ups and downs, but a great level from both."

Up next for world No.2 Medvedev is Grigor Dimitrov, who beat American Reilly Opelka 6-3 6-4 earlier in the day.

Medvedev's compatriot Andrey Rublev lost 6-4 3-6 7-5 to American Tommy Paul.

Paul moves on to face 21st seed Cameron Norrie, who beat Roberto Bautista Agut 6-4 5-7 6-3.

Playing at Indian Wells for the first time, 19th seed Aslan Karatsev upset Denis Shapovalov 7-5 6-2, saving the only break point he faced in the match.

Casper Ruud, seeded sixth, rallied past Lloyd Harris 6-7 (4-7) 6-4 6-4 as he seeks his sixth tournament title this year.

He will face 11th seed Diego Schwartzmann, who beat 18th seed Daniel Evans 5-7 6-4 6-0.

Eighth seed Hubert Hurkacz had little trouble with Frances Tiafoe, rolling past the American in straight sets.

Jannik Sinner, the 10th seed, advanced via walkover when John Isner withdrew from the tournament to fly home and be with his wife Madison with their third child expected to arrive ahead of schedule.

with DPA