Andy Murray battles into third round

The world number one’s form fluctuated wildly on Suzanne Lenglen, but he did enough to oust an opponent ranked 49 places below him.

Murray was nearly forced the distance, but broke the Slovak as he served for the fourth set at 5-3 before winning a tie-break – sealing victory with a wonderful instinctive volley at the net.

"I expected it to be very tough," Murray said afterwards.

"He goes for huge shots and on his forehand he can hit winners anywhere on the court. Sometimes you think you have hit a good shot and then he comes up with unbelievable power from a defensive position. It was very tough."

Recovering from illness and injury, Murray's relationship with the clay has turned sour this year, with early losses in Madrid and Rome.

His form has been a far cry from the run he enjoyed just a year ago, when he contested three successive finals on the slow surface and came within one match of triumphing at Roland Garros.

The 30-year-old’s next task is more ominous, with Del Potro – who Murray beat to win Olympic gold in Rio last summer – a real threat to his ambitions of going deep in Paris.

Del Potro progressed after opponent Nicolas Almagro retired from their match.

"Juan Martin has come back from some injuries and had some tough draws. I sure we'll get a good crowd and it'll be a great atmosphere," Murray said.