Andy Murray has admitted that Juan Martin del Potro proved a "tough" opponent during his 7-6 7-5 6-0 victory over the Argentine at the French Open.
The world number one, who beat Del Potro to win gold at last year's Rio Olympics, said that claiming the first set was vital in the third-round contest.
"Whoever won that first set had big momentum," BBC Sport quotes Murray as saying. "It's slow and heavy and coming back in these conditions is difficult.
"I thought I played some good tennis towards the end and I expected a tough match.
"It was tough. I think he was playing much better than me in the first set. Both of us hand some chances in the first set, the second set was the same. Both of those sets could have gone either way."
Murray will face either John Isner or Karen Khachanov in the next round.
