Russian tennis player Andrey Rublev has been criticised for his behaviour at the French Open after almost injuring a court sweeper with a ball he hit in anger following a set loss.

The seventh seed unexpectedly dropped the first set of his first-round clash against South Korea's Kwon Soon-woo, losing 6-7 (5) on a tiebreak.

Frustrated, the 24-year-old smashed a ball that ricocheted off his chair and narrowly missed a nearby court sweeper.

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The ball came within centimetres of hitting the volunteer in the head, with the force of the ball knocking his hat off.

Rublev's outburst was immediately called out on social media, with many drawing parallels with Novak Djokovic's disqualification from the 2020 US Open after hitting a line judge in the throat with a ball after losing a game.

But unlike Djokovic, Rublev simply received a code violation and was allowed to continue the match, which he ended up winning 6-7 (5) 6-3 6-2 6-4.

"I lost my mind for a moment, and of course I regret what I did," Rublev said afterwards.

"It's unacceptable to hit the ball the way I hit it.

"Better if I just hit the racquet on the seat, because the ball can affect [someone]. That's when the problem comes.

"This is unprofessional from my side and hopefully I will never do it again."

Elsewhere at Roland Garros, fellow Russian Daniil Medvedev eased into the second round after defeating Facundo Bagnis 6-2 6-2 6-2, while world number eight Casper Ruud put a swift end to the career of French favourite Jo-Wilfried Tsonga, who announced the French Open would be the last tournament of his career.

But those games were eclipsed by one of the biggest upsets in the first round, with world number 15 Denis Shapovalov losing to Danish teenager Holger Rune 6-3 6-1 6-4 7-6 (7-4).

"I didn't really show up today, so it's a little bit difficult," Shapovalov said.

"Of course, Holger is playing some great tennis. He won his first title, he's pushing some top guys.

"So not taking anything away from him, but I think against most players today, I wouldn't come out the winner."