American Ben ‘The Mountain’ Shelton became the youngest American to reach the semi-finals of the US Open after a four-set win over compatriot Frances Tiafoe on Tuesday night.

After the big-serving Shelton, aged 20, split the first two sets with Tiafoe under the lights at Arthur Ashe Stadium, the left-hander came from a break down twice in the third set to force a tiebreaker. Shelton earned two set points and led 6-4 but ended up serving back-to-back double faults to hand Tiafoe a set point. The youngster came back to win that tiebreaker and the fourth set to complete the 6-2, 3-6, 7-6(7), 6-2 in three hours and seven minutes.

The win sets up a blockbuster showdown against 23-time Grand Slam champion Novak Djokovic. It also moves Shelton into the top 20 of the world, having been ranked No 165 at this time last year.

“I think tonight was a real physical battle. You have Frances Tiafoe on the other side of the court and you have the weather that you had in there. It was pretty muggy, pretty hot. 75% of the match I think both of us were finishing points fairly tired, trying to catch our breath,” Shelton said in his post-match press conference.

“End of that third set is when I really had to dig deep. I had a set point at 6-5, went up to the line with heavy legs and ended up double faulting two times in a row. Got a little bit lucky with the slap shot to get back in control of the breaker. And then, I was just tough the last two points. I think that was the key for me tonight. Just being tough and being relentless, and knowing that I could go the distance physically no matter how bad it hurt. That was just kind of what I was sticking with.”

Friday’s semi-final will be the first meeting between Shelton and Djokovic, and the American is pumped about the opportunity to take on one of the greatest players of all time at his home Grand Slam.

“Going into the semifinals, I’m pretty pumped about the opportunity to go back out there and have the same feeling that I had today against another really tough opponent,” the former NCAA champion said. “I hope that I can bring a high level again on Friday. 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. 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.”

Not one to shy away from the big occasions, Shelton added that he plans to employ some different tactics against the three-time US Open champion. “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.”