The world number 56, who made the French Open fourth round in 2013 and 2014, twice recovered from a set down to advance 6-7 (6/8), 7-6 (7/4), 5-7, 6-1, 6-4 in just under four hours. That set was gone and, soon enough, his first appearance since 2012 at Roland Garros would be over entirely with a 7-6 (8), 7-5, 6-0 loss to Murray in the third round.
Later, del Potro got anti-inflammatory pills from a doctor to help with a bothersome groin muscle, although he said his biggest issue was Murray.
Murray needed nearly one and a half hours to nail the first set as he uppered in the tiebreak 10-8, only to see their Argentine opponent stand at the net for a while to show frustration between the interval.
Murray, who finished a total of 44 winners and converted 6 of 17 break points, prevailed in the following two sets with 7-5, 6-0.
But he rediscovered his old self on Philippe Chatrier Court in front of a crowd that never seems to warm to him as much as his opponents.More news: Charles Barkley Comments on Tiger Woods' DUI Arrest, Golf Star's 'Haters'
"I only say "Merci beaucoup" (Thank you very much) but I hope I can learn", Halep said.
The unseeded Alize Cornet took her down in straight sets, 6-2, 6-1. "I was really looking forward to the French Open", Murray said. "I didn't feel good".
"It was obviously an important win for me and a big match, because Juan, when he's playing well, is one of the best players in the world", Murray said.
The former US Open champion also had chances in the second set, but again Murray proved too strong. "I had struggled the last six or seven weeks coming in".
The 2014 U.S. Open victor, who warmed up for the year's second grand slam by capturing his first claycourt title in five years in Istanbul last month, delivered a near-perfect performance to equal his best-ever showing in Paris.
Prevailing in a tense two hour, 53-minute test, Murray advanced to the French Open fourth round for the eighth time. I think that was the reality of it today was there was a few points here and there. I have been playing great, great points during whole the first set.More news: World leaders vow to defend climate pact
Of course, Murray is expected to find greater opportunities to thrive in the second half of the season on grass of Wimbledon and the hard courts of North America.
His major titles have come on faster surfaces at Wimbledon and the U.S. Open, but Murray was the French Open runner-up past year.
Murray leads the 29th-seeded Del Potro 6-3 in head-to-head matches, but this is their first meeting in a major since Murray's win at the U.S. Open quarterfinals in 2008.
Xu and Canadian Gabriela Dabrowski, the No. 9 seeds, only needed 55 minutes to win 6-1, 6-2 against Madison Brengle and Anna Smith.
Romania's Simona Halep raises her fist as she defeats Russia's Daria Kasatkina during their third round match of the French Open tennis tournament at the Roland Garros stadium, Saturday, June 3, 2017 in Paris.More news: US employers add modest 138K jobs; jobless rate dips to 4.3 percent
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