Shelton, a former college star who only turned professional last year, surpassed his breakout performance in Melbourne on Tuesday by knocking out Frances Tiafoe to reach the last four in New York.

The youngest American men's US Open semifinalist since Michael Chang in 1992, Shelton's success at Grand Slams has masked an otherwise challenging first full season on the ATP circuit.

In between the two majors which bookend the tennis calendar, he went 18 straight tour-level events without winning back-to-back matches.

But Shelton attributed his victory over Tiafoe partly to the growing pains that have strengthened his resolve as he charts his path on the tour.

"I think I've definitely made some strides physically being out on tour a full year and playing a lot of matches and just being on the court more, working hard in the gym," said Shelton, beaten in the first round of last year's US Open as the world number 165.

"My fitness levels have surely improved, and I think all that together is kind of what happened (Tuesday)."

He celebrated by pretending to answer a phone call before hanging up – a signature move of friend and three-time 110m hurdles world champion Grant Holloway. "For me it's kind of like I'm saying I'm dialed in," he said.

Ten of Shelton's 17 wins in 2023 have come at the Grand Slams, and he is the last remaining hope this week for a country without a men's major winner since Andy Roddick won the US Open 20 years ago.

"Going into the semifinals, I'm pretty pumped about the opportunity to go back out there and have the same feeling that I had (against Tiafoe), you know, another really tough opponent," said Shelton.

"I have been enjoying every minute on court, interactions with the crowds and just the tennis that's being played. So I hope that I can bring a high level again on Friday."

- Sporting stock -

American football was Shelton's first love, but the former quarterback called an audible aged 12 to follow in the family tradition – father Bryan and late uncle Todd Witsken both played tennis professionally.

Bryan Shelton coached his son to the 2022 college title at the University of Florida, and is now in his corner with Ben emerging as one of the sport's budding stars.

Shelton had never left the United States before touching down in Australia in the new year. He was seeded at the French Open and Wimbledon but his ranking slipped to 47th ahead of the US Open.

He is guaranteed to crack the top 20 for the first time next week, what he hopes is a mere stepping stone on his way towards the summit.

Shelton will get an up-close glimpse of what it takes to reach the top when he faces 23-time Grand Slam champion Djokovic for the first time.

"Definitely a tough challenge. I think that whenever you play somebody for the first time and someone who has been in this situation so many times and come out victorious so many times, that's in the back of your head," said Shelton.

"You just know how rock solid the guy is and how mentally tough, how physically tough. So that's definitely something that I have to game-plan for."

Shelton held his own in a straight-sets loss to Carlos Alcaraz at Cincinnati last month. He is counting on the element of surprise to unsettle Djokovic.

"I also think that it's an advantage with my game style playing someone who's never played me before," said Shelton.

"I think that I can bring some things to the table that maybe you don't see in your normal match that you play on the ATP Tour.

"So I'm definitely going to try to bring some things to the table that are different and hopefully disruptive on Friday.