NEW YORK — With his big smile, charismatic personality and a rocket left-handed serve that reached 149 mph, Ben Shelton became one of the breakout stars of the U.S. Open.

The 20-year-old Shelton, who was born in Atlanta and won the 2022 NCAA singles championship at the University of Florida, defeated two older, more established Americans — No. 14-ranked Tommy Paul and No. 10 Frances Tiafoe — on his way to becoming the youngest American man to reach the U.S. Open semifinals since 1992. John McEnroe called him a “breath of fresh air” for American tennis.

His reward in the semifinals?

A date with No. 2-seed Novak Djokovic, a 23-time Grand Slam champion who arguably is the GOAT of men’s tennis.

And that’s where Shelton’s run ended Friday. Djokovic, 36, strategically dismantled Shelton, 6-3, 6-2, 7-6(4), in front of some 24,000 fans. The roof in Arthur Ashe Stadium was closed for the match because of lightning in the area.

Djokovic advanced to Sunday’s final, where he will play the winner of the second semifinal between world No. 1 Carlos Alcaraz and No. 3 Daniil Medvedev. He is seeking his fourth U.S. Open title in his 10th finals appearance.

“This is the kind of atmosphere that we all like to play in, so I’m really, really pleased with this win today,” Djokovic said on court. “Another Grand Slam finals, I cannot be happier with obviously where I am.”

Djokovic won the first two legs of the calendar Slam at the Australian Open and French Open before losing to the 20-year-old Alcaraz in five sets in an epic Wimbledon final.

Djokovic was playing in a men’s-record 47th Grand Slam semifinal, while Shelton was competing in his first after reaching the Australian Open quarterfinals in January. Djokovic has reached 36 major finals in the 72 Slams he has played. He has won his past 31 matches against American opponents, including 15 at majors.

Despite the long odds coming in, Shelton said in a pre-match interview with ESPN, “I’m not feeling too nervous today. I’m ready to get out there and just compete.

He added: “I think everything that’s happened in my life so far has prepared me for these type of situations, and I’m ready for it.”

But few players are equipped to deal with Djokovic, who is playing maybe the best tennis of his life. With one more win, he will surpass the great Serena Williams and tie Margaret Court for most all-time with 24 major titles.

“I think he’s better than he’s ever been,” John McEnroe said of Djokovic on ESPN. “I’m not going to say he’s moving better but as a complete player, the whole package.”

Shelton showed his inexperience early when he played a loose game and was broken in the sixth game of the first set, missing a volley wide to fall behind 4-2. Djokovic closed out the first set in 33 minutes.

In the second set, Shelton again appeared to show some nerves, double-faulting to fall behind a break at 3-2. When Shelton sprayed a backhand wide at the net, he fell behind a double break at 5-2. Shelton never was able to threaten Djokovic on the Serb’s serve, and Djokovic served out the second set for a two sets to love lead.

But Shelton showed signs of life, breaking Djokovic late in the third and then holding with a 145-mph service winner for a 5-4 lead, causing the crowd to roar in support of the American. Shelton held a set point on Djokovic’s serve, but the Serb escaped with a 124-mph service winner of his own.

Serving at 5-all, Shelton became unglued and sprayed two of his 24 forehand errors wide, allowing Djokovic to break for a 6-5 lead. Shelton fought off a match point on Djokovic’s serve and forced a break of his own to send it to a tiebreak.

Unfortunately for him, Djokovic is a virtual lock in tiebreakers.

On match point in the breaker, Djokovic closed it out when Shelton sent a forehand into the net. The two briefly shook hands at net, and Djokovic raised his hands and bowed to the crowd. The crowd applauded Shelton as he walked off the court.

Shelton was coached at Florida by his father, Bryan Shelton, a former tour pro and women’s tennis coach at Georgia Tech who left the college coaching ranks to focus on his son. He was in Shelton’s box coaching him during his U.S. Open run.

“I think Ben’s mom and I, super proud, that he’s just handling himself so well,” Shelton said Thursday. “You know, first off the court and then on the court.

“Our hope for him is that he would just continue to grow as a person and as a player out here on the tour over the last year, and I think he’s done that.

Djokovic credited college tennis with helping prepare Shelton — now up to No. 19 in the live rankings from No. 47 entering the Open — for the pro tour.

“I think it’s great,” the Serb said earlier in the tournament. “It’s great that Ben Shelton, for example, a player who came from college tennis, is playing at the highest level, producing some amazing tennis. I think it’s a great message for all the players who want to go to college, but then still keep on playing professionally. It proves that it is possible, which maybe up to 15 to 20 years ago, it was completely different.

“I think the college tennis level has increased incredibly, and Ben is a great example of that. I think it’s great. It’s great for attention towards the tennis, towards the U.S. Open. It’s important that we have American players doing well.”

Not well enough to win majors, though.

Among the men, no American man has won one since Andy Roddick at the U.S. Open in 2003, 20 years and 78 majors ago. A huge reason is that Djokovic, Roger Federer and Rafael Nadal — three Europeans — have won 65 of the past 80 majors, and Djokovic is looking to add to that total Sunday.

Still, for the first time since 2005, three American men – Shelton, Tiafoe and No. 9 Taylor Fritz – reached the U.S. Open quarterfinals.

Shelton was among five American men and women to reach the quarterfinals this year. Four of those – Coco Gauff, Madison Keys, Tiafoe and Shelton – are players of color. Gauff will play for her first Grand Slam singles title Saturday against Aryna Sabalenka, while Keys lost in the semifinals.

“In my opinion, he’s going to be around at the end of majors for years to come” McEnroe said of Shelton, whom he picked as the final player for the world team in the upcoming Laver Cup.

“He made a great step forward in this tournament, he should be extremely proud of his success.”