Casper Ruud got to the French Open final in May, but was humble enough to realize he may never do anything as big again. 

Now, however, he’s on the verge of just that. The fifth-seeded Norwegian exhibited his heavy top-spin forehand Friday night and advanced to the U.S. Open men’s finals with a 7-6, 6-2, 5-7, 6-2 victory over Russian Karen Khachanov. 

“I’m so happy,’’ said Ruud, who will face Carlos Alcaraz on Sunday in the final. “After Roland Garros, I was extremely happy but humble enough that it could be my only final at a Grand Slam in my career. And here I am back a couple of months later.” 

Yes, here he is. No Norwegian had ever so much as made it to an Open quarterfinal until this fortnight. 

“This is probably the biggest match of both our careers,’’ said Ruud, whose victory was highlight by winning a 55-shot rally on set point. “I was fortunate to win the first set that helped my nerves.’’ 

Ruud is not as flashy or athletic as Tiafoe or Alcaraz, but more of a rock. 

“The main thing, obviously his consistency, his way of defending,’’ Khachanov said. “As soon as you give him the space to step in, he’s really fast to go around his forehand, play aggressive as well.’’ 

Ruud got off to a 2-0 start, breaking Khachanov promptly. But the Russian bounced back to get it back on serve at 2-2 and they headed to a tiebreaker. 

In the extra session, Ruud went up 6-3 before Khachanov saved two set points to bring it to 6-5. 

That’s when they engaged in one of the longest points ever at the Open — and officially the longest of this fortnight. 

The duo combined for 55 shots, all baseline bashes, lasting 1:15. 

Neither player ran the other one much during the historic rally, but Ruud amped it up at the close. Ruud crushed a backhand down the line to end the marathon point and take the first set. 

“I think I’ve never had a rally 55 shots,’’ the Russian said. “That was a crazy rally. I felt pumped in a way that we had this long rally and were moving each other. Actually a few games after showed me it was not that good, the long rally.’’ 

If it was the 55-shot rally or not, Khachanov appeared spent to start the second set. Ruud cruised to a 6-2 triumph to take 2-0 lead. 

This seemed headed toward a straight-setter but Khachanov, who upset Nick Kygrios, arose late in the third set, breaking Ruud as the Norwegian served at 6-5. 

Ruud buckled down and romped in the fourth set, ending it on a drop shot after moving his opponent off the court with blistering inside-out forehands. 

Khachanov, the No. 27 seed, said he’ll take his semifinal showing as he now faces an uncertain fall with talk some European events may ban Russians. Khachanov said he is heading home to Dubai and declines to “read the news’’ nowadays.