Frances Tiafoe will face fellow American Taylor Fritz in the final of the Japan Open in Tokyo.
Tiafoe sealed the opening set of his semi-final in comfortable fashion but did not win a game in the second against South Korea's Kwon Soon-woo.
He then raised his game before completing a 6-2 0-6 6-4 victory.
Fritz was involved in a hard-fought match against Canada's Denis Shapovalov in the other semi-final, but emerged a 6-3 6-7 (5-7) 6-3 winner.
Tiafoe, who was beaten by eventual winner Carlos Alcaraz in the semi-finals of the US Open in September, said: "It was a weird match, but happy to get through.