NEW YORK — Taylor Fritz, the late son of an American tennis star from the 1970s, is going to the final of the US Open to face Jannik Sinner.

Thanks to his big serve, growing toolbox and stronger backbone, which have allowed him to compete with the world’s best players in recent years, Fritz twice fought back from a set down against Frances Tiafoe, his close friend and teenage training partner.

“He overwhelmed me from the baseline,” Fritz said on the court. “I told myself I had to stay and fight.”

And he listened.

In the first US Open semifinal between two American men in 19 years, Fritz triumphed 4-6, 7-5, 4-6, 6-4, 6-1. He is the first American to reach the US Open final since 2006, when Andy Roddick lost to Roger Federer.

Fritz will be a heavy underdog on Sunday against Sinner, the Italian world number 1 who has largely defeated his opponents in the past two weeks, despite the occasional wobble. But Fritz has been picturing himself as the winner of the US Open trophy for years, even though the idea seemed ridiculous to most.

He didn’t give a damn what was happening on the other side of the net. He would let Sinner, Carlos Alcaraz and Novak Djokovic all play at once for a chance like this.

“It’s the reason why I do what I do, the reason why I work so hard,” Fritz said through tears on the court when it was over.

Taylor Fritz blew away Frances Tiafoe in the final set. (Kirsty Wigglesworth / Associated Press)

On this court, in this stadium, in front of a crowd of nearly 24,000, with his home Grand Slam on the line and the chance to break the 21-year drought for American men at major tournaments, don’t think he’s not fancying his chances.

Quiet, humble, he’s so confident these days, and he’s played that way for the past 12 matches, taking down Alexander Zverev and Casper Ruud, both Grand Slam finalists before him, en route to a semifinal against Tiafoe — an overwhelming crowd favorite who thrives on the vibes of Arthur Ashe Stadium, especially at night.

Two years after beating Rafael Nadal en route to a glittering New York performance with a stunning five-setter against Alcaraz, Tiafoe on Ashe under the spotlight at the US Open has become a thing – for him and for everyone who shows up.

Frances Tiafoe surprised the crowd on Arthur Ashe — for most of the match. (Associated Press)

No matter how much Tiafoe’s decline has been in recent months, and how disappointing his play has been over the past year, he sees the bright lights of the city and the big stadiums, hears the noise and looks up at the big screens to see which of his famous idols, now friends, are there.

He comes alive because “things are different on Ashe.”

Not against Fritz.

Those were Tiafoe’s words earlier this week after securing his spot in the semifinals against the 26-year-old from Southern California, who has dominated their matchup for eight years. Fritz had beaten Tiafoe six out of seven times, and now it’s seven out of eight.

For most of Friday night, it wasn’t clear why. Fritz had the best serve, but Tiafoe nearly matched it and seemed to have only a few more strokes in his racket. That’s what the match came down to — a few points in each set. For starters, Fritz played the sloppiest at the worst times.

And then, late in the fourth set, with Tiafoe serving to tie the score at 5-5 and inches closer to the finish, he had one of those lulls that have plagued him his entire career, on the biggest stage at the worst possible time. Double faults, mistakes, bad decisions. When a mistake had to be made, Tiafoe made it, and Fritz jumped at the moment and finished Tiafoe with the ace that put him one step away from where he always wanted to be.

A handful of points can make or haunt a player’s career. For opposite reasons, Tiafoe and Fritz will not soon forget the last five points of the fourth set.

“It’s hard to swallow,” Tiafoe said. “This one’s going to hurt really bad.”

After leveling the set and turning up the pressure on Fritz, Tiafoe made two double faults, allowing Fritz to get back into the match at 40-40.

Then he hit a forehand far out of bounds. Suddenly he had a point, Tiafoe did what players always do when they suddenly lack the will or confidence to fight through a point. He tried to escape it early.

The drop shot was doomed to fail as soon as it left his strings, landing meekly in the bottom of the net.

By now, Tiafoe was getting cramps in his body and he didn’t know why. “Shut down,” he said.

“It probably had a lot to do with nerves. I couldn’t really move.”

And so, after two hours and 51 minutes, there was a battle between Fritz and Tiafoe, comrades at national junior training camps when they were teenagers, and a place in the final of their own Grand Slam.

Fritz clenched his fist and sat down in his chair, organizing himself like a manager preparing for an important meeting.

Tiafoe took off his shirt, leaned back and looked up at the sky, unable to understand how he could have let this slip. He gargled pickle juice. He ate. He drank. Anything to suppress the cramps.

Fritz then put his foot on his old friend’s neck, though he hardly had to apply any pressure. He won the next seven points and the next four games. Tiafoe never held his serve again.

For the better part of two sets and 90 minutes, Fritz had been able to do little more than hold on and hope that Tiafoe’s level would drop, as almost always happens in a five-set match. Now it did drop, even as the crowd tried to catch him on the way down.

It was hopeless. Fritz won 25 of the 34 points in the final set. Tiafoe won only four points on his serve, and none of the nine that started on his second serve.

When Fritz double-faulted to return a break of service in the fifth game, he looked at his box, spread his hands apart, palms down on the floor, and raised and lowered them like lungs. Calm. Calm. He then laughed and went on to make the final.

Taylor Fritz held his nerve long enough to take Frances Tiafoe’s incredible tennis down a level. (Kena Betancur/AFP via Getty Images)

That’s not where anyone thought he would be ten years ago, when he wasn’t even good enough to train on the first courts with the best players at the USTA training camps in Florida. Tiafoe, and Tommy Paul and Reilly Opelka were on those courts. Fritz was relegated somewhere else.

When he got home to California, he told his mother, Kathy May, a two-time U.S. Open quarterfinalist, how embarrassed he had been. The other boys were so much better.

He used it as motivation then, and he’s been playing to prove something ever since. His biggest chance comes Sunday, when few give him a chance against Sinner at the end of one of the biggest weekends in American tennis in decades.

On Saturday, Jessica Pegula, the daughter of Buffalo Bills co-owners Kim and Terry (and Buffalo Sabres owner Terry), will face Aryna Sabalenka in the women’s final. Like Fritz, whose mother is heir to the Macy’s retail fortune, Pegula comes from one of the wealthiest families in the country. They had a lot of advantages growing up, but also a lot of doubters. They could have listened. They could have decided there were easier ways to spend their time. They could have lived a life of leisure.

They didn’t. They chose to compete in the world of professional tennis, with no prisoners. Whether they win or lose this weekend in their home Grand Slam, they will at least get a share of the reward they have been seeking for some time.

(Top photo: Jamie Squire/Getty Images)