He knew the opener was key in the slow, heavy conditions and by the third set, he was on the ropes, winning just 11points. Del Potro knew as much, and so did Murray.
In a titanic first set, Del Potro wasted 4 set points then saved two before Murray pounced when the Argentine star narrowly miscued.
Crestfallen, the 2009 US Open champion rested his hands and head on the net for nearly the entire duration of the changeover before handing Murray the break in the opening game of the second set.
But his third round meeting with old foe Juan Martin Del Potro today gives him the chance to lay down a marker and show he is on his way back. "I did not grow up with brothers, only sisters and we all say "she" more than "he"'".More news: The Zpg Plc (ZPLA) Earns Buy Rating from Shore Capital
Murray eventually took it 10-8 after one hour and 25 minutes, with Del Potro then spending much of the changeover slumped over the net.
Wawrinka, owner of three major championships in all, will play for a quarterfinal berth against No. 15 Gael Monfils or No. 24 Richard Gasquet, a pair of Frenchmen whose third-round match was interrupted by rain in the first set Saturday.
"I'm starting to feel better".
"Whoever won that first set had big momentum", said Murray, who beat Del Potro in the Olympic gold-medal match at last year's Rio Games.
Victory will come as light relief for Murray, who has struggled on all surfaces since the turn of the year. After walking up to check the ball's mark on the clay - a line judge and the chair umpire confirmed it was out - del Potro leaned forward on the net, head bowed, the very picture of despair.
When is Murray vs Del Potro and where can I watch it?More news: Trump Admits He's Under Investigation, Attacks Deputy AG Rosenstein
Having twice stopped his opponent from taking the opening set, Stan Wawrinka dispatched Fabio Fognini like a gentle breeze does humidity, winning 7-6, 6-0, 6-2 to advance.
And older brother Jamie said: "He has had a rough year from a results point-of-view but also because his health has not been good at all". "The most important thing is to get through the matches and gaining the confidence of getting through tough situations and coming through".
It was disappointment, however, for British number two Edmund, as he lost out to Kevin Anderson in five sets.
"Kyle is a great player and it came down to one or two points", said Anderson, who next faces Marin Cilic, who is yet to drop a set en route to the second week.
Also, Spaniard Fernando Verdasco qualified for the fourth round after beating Pablo Cuevas, world no. 23.
She eased past Russian 14th seed Elena Vesnina 6-4, 6-4 in a match which featured a 17-minute service game, punctuated by 11 deuces, for the Russian in the second set.More news: Stephen Curry's 2nd NBA championship puts him in rare company
The South African, 31, fought back to win 6-7 (6-8) 7-6 (7-4) 5-7 6-1 6-4 in a near four-hour match.
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