New York, New York - Carlos Alcaraz is having a remarkable breakthrough season, and he has a chance to put an exclamation point on it after defeating Frances Tiafoe 6-7 (6-8) 6-3 6-1 6-7 (5-7) 6-3 in Friday's US Open semi-final.

It will be 19-year-old Alcaraz's first appearance in a grand slam final, and with a win against Casper Ruud, he will also become the youngest world number one in men's tennis history, beating out Lleyton Hewitt (20 years and nine months old) by over a year.

In a tight first set where both athletes failed to capitalize on their break point opportunities, Tiafoe saved an Alcaraz set point to force the tiebreaker, where he would finally secure the opening frame with the fourth set point of his own.

With such fine margins deciding the outcomes, some sloppy serving would flip the script in the second set. After Tiafoe had no double faults in the first and Alcaraz had three, it was Alcaraz cleaning things up to post zero for the rest of the match.

Meanwhile, Tiafoe had a pair of costly double faults in the second, which ultimately led to the only break in the set, as Alcaraz converted one of his four opportunities, while saving the three break points he faced.

Tiafoe's vaunted serve continued to meltdown in the third frame, dropping his first-serve accuracy from 67% to 30%, which led to him winning just 35% (seven-of-20) of his service points as Alcaraz lifted.

Alcaraz needed only 34 minutes to wrap up the third set, thanks in large part to Tiafoe committing 12 unforced errors with only six winners, as the Spaniard finished the set with just one ace and four winners.

As the double faults and unforced errors faded away, Tiafoe rediscovered the kind of form and fight that saw him stylishly handle the challenge of Rafael Nadal earlier this week. Tiafoe and Alcaraz traded breaks in four consecutive games in the fourth set, with the American having to save a match point to force another tiebreaker where he would prevail.

But Alcaraz would not be denied, grabbing a crucial break in the opening game of the fifth set, and when Tiafoe snatched it back, his joy was short-lived as Alcaraz re-broke in the very next game to-love, and once more to finish the match.