It had been three years since del Potro, beset by wrist injuries, played on center court at a grand slam.
Athletes often utter they don't know when their careers might end or be severely hampered with an unexpected health issue, but the phrase, for many, comes off as an emotionless cliché. Young ones, especially, possess a feeling of invincibility.
For del Potro, however, it became a reality. Indeed, he is tennis' most unfortunate example of a grand slam winner whose career nosedived through no fault of his own.
Tipped to shake up the "Big Four" after winning the 2009 U.S. Open weeks shy of his 21st birthday, his misery began the following campaign.
Del Potro -- who has undergone one surgery to his right wrist and three to his left -- has contested a mere 34 matches since the start of 2014.
Playing Wawrinka in the second round -- the first time two grand slam winners met at that early stage at Wimbledon since 2008 -- it marked his second match at a major since early 2014.
Meantime, Wawrinka had overtaken the 6-foot-6 "Tower of Tandil" by winning grand slam titles at the Australian Open in 2014 and French Open last year.
Del Potro's career might continue to drift because of the wrist in the years ahead, but on Friday there was respite, a moment to savor on tennis' most famous court. He defeated Wawrinka 3-6 6-3 7-6 (7-2) 6-3 under the roof to move into the third round. Serena Williams and Venus Williams escaped, meanwhile, against the younger duo of Christina McHale and Daria Kasatkina, respectively, as rain continued to play havoc with the schedule.
The rain prompted organizers to schedule play for the middle Sunday -- usually a day off -- for the first time since 2004.
But Novak Djokovic -- the winner of four straight majors -- incredibly trailed Sam Querrey by two sets 7-6 (8-6) 6-1 when they were forced off Friday evening by, of course, that rain.
Back to del Potro. "My hands are shaking," he said. "I feel alive."
A gracious Wawrinka, while disappointed in defeat, couldn't help but praise del Potro.
"For sure we are all happy that he's back," the Swiss told reporters. "He's a great guy off the court. He's an amazing player on the court. He's a big champion. He was so unlucky with all the injuries he had for many years.
"We just all hope that he can be free of injury now and play well this year and the next year."
Del Potro recorded his first top-five victory since defeating Rafael Nadal at the Shanghai Masters in 2013, even in being weakened on his backhand. In trying to protect the left wrist, del Potro now slices -- largely a defensive or neutralizing shot -- the overwhelming majority of his backhands.
And when he does drive through the backhand, it lacks the power and pace of years past. The serve and forehand are considerable weapons, the latter thought by some to be the biggest forehand ever.
The book on del Potro now, then, is to go to the backhand, but Wawrinka appeared to overthink in that respect, targeting the backhand when, at times, the right shot was to send the ball the other way with the court exposed.
It happened, for example, on two points in succession when Wawrinka was broken to begin the third.
Wawrinka already blundered by playing a sloppy second set to give del Potro belief he could triumph, and the belief soared when the 27-year-old grabbed the third-set tiebreak in lopsided fashion.
A shaken Wawrinka was broken in the eighth game of the fourth and del Potro served the affair out to the crowd's delight. So much for Wawrinka's grass-court collaboration with former Wimbledon champion Richard Krajicek.
Drama for Williams sisters
Serena Williams' streak of never losing before the third round at Wimbledon was threatened by McHale, before the world No. 1 progressed 6-7 (7-9) 6-2 6-4 on Centre Court. Serena thought she wrapped up the first at 5-4 against the world No. 65 when McHale's heavy forehand was called long. Both players inched closer to their chairs but McHale challenged anyway -- and was proved right by the narrowest margin.
When she proceeded to claim the 16-point tiebreak, Williams, seated, flung her racket behind her and in the direction of a cameraman. She, too, whacked her racket into the ground five times to earn a warning.
After comfortably winning the second, Williams found herself in a battle in the decider. Locked at 4-4, the ninth game was filled with one dramatic point after another. McHale opened the door to Williams with a double fault; the 24-year-old won a 25-shot rally to get to 30-all; but then struck another double fault on game point.
The 21-time grand slam winner broke for 5-4 and without much fuss closed out McHale, her legendary serve kicking in.
Venus Williams advanced 7-5 4-6 10-8 over 19-year-old Daria Kasatkina -- who won their duel in Auckland in January.
Kasatkina, though, showed tremendous poise after emerging from a rain delay of one hour, 13 minutes. The first point she played on the resumption was a match point against her at 6-7, 30-40, and the Russian forced Williams into an error. The elder Williams sister finally prevailed 20 minutes shy of three hours.
Their match lasted longer than Nick Kyrgios' five-set, two-hour triumph over Dustin Brown.
Wawrinka's compatriot Roger Federer crushed a British player -- this time Dan Evans 6-4 6-2 6-2 -- after seeing off cult hero Marcus Willis in the second round.