Novak Djokovic is one win away from becoming the first man to complete a Grand Slam in 52 years.
The world number one fought back to defeat Alexander Zverev 4-6 6-2 6-4 4-6 6-2 Friday in the US Open semi-finals to put himself on the brink of history.
Djokovic will face second seed Daniil Medvedev in Sunday's final as he attempts to win a record 21st grand slam title and become the first man since Rod Laver in 1969 to win all four majors in a calendar year.
Laver was in attendance at Arthur Ashe Stadium to watch the top seed exert his will as he has done in so many five-setters over the years, breaking down the younger player over the course of the match to emerge with yet another triumph.
Zverev had ended Djokovic's chances of a Golden Slam with a semi-final win at the Tokyo Olympics, rallying for a three-set win after dropping the opening set, but the script was different Friday.
It started with Djokovic losing the opening set for the fourth successive match in New York. In the previous three rounds, he did not drop more than three games in any subsequent set, but Zverev made him work harder this time.
With the first set even at 4-4, Djokovic fell behind 15-40 and double faulted on break point to give Zverev the opening he needed. Though his next service game was a bit shaky, Zverev managed to take the set when Djokovic mis-hit a forehand.
The German's momentum did not last, though, as he returned the favour by double faulting on break point in his first service game of the second set and watched Djokovic level the match with relative ease.
Zverev had a chance to take control early in the third, earning two break points at 2-2, but he failed to convert and did not get another chance. When Djokovic had a similar opportunity up 5-4, though, he closed it out.
Down 0-40 in that game, Zverev saved two break points – the latter via an epic 53-shot rally that was the longest at this year's US Open – but Djokovic slammed home an overhead winner on the next point to take the set.
Zverev shook off that disappointment and put the pressure back on Djokovic by hammering a forehand winner down the line to break the top seed and take a 2-1 lead in the fourth.
The German did not falter the rest of the set, eventually serving it out to force a decider and push Djokovic to a fifth set for the first time since the French Open final against Stefanos Tsitsipas.
Djokovic jumped to an early lead in the fifth, forcing Zverev to the net on break point in the second game with a beautiful drop shot before finishing the younger player off with a cross-court winner.
Djokovic reeled off four consecutive points to break Zverev in his next service game, then held at love to put the fourth seed on the brink at 5-0.
Zverev, a winner in seven of his previous eight five-setters, did not surrender, breaking Djokovic thanks to a double fault on game point to pull within 5-2.
But Djokovic ended it there, breaking back to close out the match in the next game as Zverev sent a forehand into the net from the baseline.
With the victory, Djokovic improved to 34-2 in night matches at Arthur Ashe Stadium and 36-10 in five-set matches in his career, winning his last seven in a row.
Djokovic – 41/49
Zverev – 49/50
Djokovic – 12/2
Zverev – 16/8
BREAK POINTS WON
Djokovic – 5/8
Zverev – 3/12