In the moment, it seemed like a joke. Trailing 4-5 in the first set of a match in Australia, Lleyton Hewitt served to Kansas City’s Jack Sock. The ball was called wide, so Hewitt prepared for his second service.

jack-sock2_400px“That was in if you want to challenge it,” Jack said.

The chair umpire did a double-take. A second later, a stunned Hewitt chuckled, as if he thought Jack was kidding. So did the crowd. But Jack urged him two more times, “Challenge it.”

With a look of “What the heck?” the Aussie said, “Yeah, I’ll challenge it,” which drew an even louder laugh from the crowd. When the replay showed the ball hitting the line, Jack gave the thumbs up. The audience cheered, and the Australian announcer declared, “Good on you, Jack.”

6-jack-sock-australian-open-16_500pxAnd that seemed to be that enroute to Hewitt’s 7-5, 6-4 victory.

You could argue that the “good” of that moment has clung to Jack. Though many of his professional colleagues skipped the Olympics because of the threat of the Zika virus and the event’s proximity to the U.S. Open, Jack was all in.

“I would have come down here with anything but a broken bone,” he told reporters in Rio, calling the Olympics, “the coolest thing I’ve ever been a part of.”

He arrived in Rio, not with broken bones, but a case of walking pneumonia. He not only battled through the illness but triumphed, earning a gold medal in mixed doubles with Bethanie Mattek-Sands and a bronze in men’s doubles with Steve Johnson.

17-jack-sock-rio-olympics_500px“Definitely a moment we’ll never forget,” he told reporters after winning the gold medal, “and something we’ll always share together.”

Less than a month later, Jack was the last American standing in the U.S. Open, upsetting 2014 champ Marin Cilic before falling to Jo-Wilfried Tsonga in the fourth round.

“Obviously I wanted to win and keep playing, but there’s going to be another one in a few weeks, another tournament, another match,” Jack told reporters at the Open. “I can improve and keep going. That’s a positive thing about tennis.”

Many would count Jack Sock as a positive for tennis. Despite his run of success, the YouTube video of his lighthearted urging for a challenge vastly outstrips his Olympic or U.S. Open moments, collecting more than 1.5 million views.

Which just goes to show that sportsmanship strikes a powerful and lasting chord, especially when delivered with a smile.