Jannik Sinner has cemented his place as the best player in the world.

This year, he’s reached world No. 1, won two Grand Slams, the ATP Finals and five other titles, and he helped Italy retain their Davis Cup crown.

But he wasn’t always a dominant threat on the tour. When Sinner was just a teenager, he beat Steve Johnson and had the former No. 21 feeling so ashamed of the match that he immediately wanted to retire.

Five years ago, a 17-year-old Sinner made a statement when he received a wildcard into the Masters 1000 in Rome and upset Johnson in the first round. At the time, the Italian was ranked at No. 263 in the world while Johnson was in the top 60.

Sinner stormed back to win 1-6 6-1 7-5, winning the last five games in a row after the American served for the match in the decider. The current world No. 1 had played just two ATP matches before that, though he’d recently won Challenger and Futures tour titles.

And Johnson was so embarrassed by his defeat that he wanted to quit tennis. The 34-year-old recalled the match on his Nothing Major podcast, admitting he knew nothing about Sinner at the time.

“I don’t know if you guys ever felt this, you play like a local wildcard or a hometown kid and there’s different feelings you have,” he said while in conversation with fellow former pros John Isner, Sam Querrey and Jack Sock.

“So I walk out there and the kid’s like 6’3, 112 pounds, like super skinny and you’re just like, ‘Oh, this could go bad for me. You gotta win, right?’ Because this is a bad look on centre court.”

After breezing through the first set, Johnson played “horrible tennis” and suddenly found himself in trouble. He continued: “And then the third set rolls around.

“I’m just like, ‘Please win, you’ve got to win this, just find a way.’ I either serve for the match or had match points and then lost 7-5.”

The defeat took a toll on the four-time title winner, who thought Sinner had no future. “I called my agent, and my coach wasn’t even there at the time, he was flying in the next day, but I’m like, ‘I just lost to - this kid sucks, he’s terrible. I’m literally quitting tennis for the rest of your life.’”

While Johnson didn’t see Sinner’s potential, his team did. He explained:started talking to my agent, couple of the other coaches, they’re like, ‘Give it time. This kid is going to be unreal.’

“I’m like, ‘You guys are so stupid, this guy is never going to make it anywhere. He’s going to have one win and it’s going to be me. This is never going to change.’”

But the American is happy to admit he was wrong about the two-time Major winner. “Little did I know like four years from then, he’s going to be making $100 million a year winning Slams and being by far and away the No. 1 player.”

Johnson didn’t retire after that match against Sinner. The former No. 21 only hung up his racket this year, playing his last match in Indian Wells alongside Tommy Paul in doubles.