The Serbian was leading 6-3 3-1 at that stage and was cantering to success in windy conditions on Philippe Chatrier court.

Earlier, Del Potro, the fifth seed, had to endure two stoppages for rain before easing through at the expense of France’s Michael Llodra.

The Argentinian was a comfortable 6-3 6-3 6-1 winner on Court One but the inclement Paris weather tested his patience.

Beginning their match under grey skies, the players went off after 20 minutes of action – at 11.30am local time – with Del Potro 3-1 ahead.

He resumed two hours later to take the first two sets but went off for a short five-minute spell as another shower came and went.

Del Potro breezed through the third set to clinch a round-two clash with either Lukasz Kubot or Viktor Troicki.

The 20-year-old has never gone further than the second round in Paris but after a breakthrough summer in 2008, he has suddenly become a danger at Roland Garros and is more at home on clay nowadays.

“I’ve played in Masters Series events (on clay) and my results were good, but a grand slam gives you a unique feeling,” he said.

“I feel good. What I did well is play well in the moments I had to, and that was enough.”

France’s Monfils, the 11th seed, has come to Roland Garros nursing a knee injury but he showed no effects of that as he swept past American Bobby Reynolds 6-2 6-3 6-1.

Monfils is one of three Frenchmen in the top 11 of the rankings, along with Gilles Simon and Jo-Wilfried Tsonga.

Rainer Schuettler was the only seed to be eliminated on the third day.

The German, a semi-finalist at Wimbledon last year, was in danger of being hit by a triple bagel by Marc Gicquel as he headed into the third set without having won a game.

The 27th seed went on to save face but still lost 6-0 6-0 6-4 to the Frenchman.

Other winners in the first round today were Victor Crivoi and Andreas Beck, while Spain’s Daniel Gimeno-Traver progressed after opponent Evgeny Korolev retired mid-match with an ankle injury.