Japan's Kei Nishikori saved two match points in his 4-6 7-6 (7-3) 6-3 semi-final victory over Luxembourg's Gilles Muller at the Swiss Indoors in Basel and will take on Croatia's Marin Cilic for the title.
The third-seeded Nishikori needed two hours and 15 minutes to overcome the big-serving Muller and run his career record against the southpaw to 3-0.
The Japanese world No.5 won just 47 per cent of his first-serve points in the first set, which he lost after dropping two service games.
Muller then had two match points in the 10th game of the second set, but Nishikori held his nerve to scrape through that set and then convert the lone break chance he created in the third en route to victory.
"Gilles is a great server and I wasn't making many returns today," Nishikori said.
"I made a lot of unforced errors to lose the first set."
Next up for the Japanese star will be the fourth-seeded Cilic, who rallied to defeat German qualifier Mischa Zverev 4-6 7-5 6-3 in the second semi-final.
Sunday's (Monday AEDT) contest will be a rematch of the 2014 US Open final, which Cilic won to capture his lone grand slam title.
Nishikori leads the head-to-head battles with Cilic 7-4.