David Goffin of Belgium rallied from a break down in the third set to upset defending champion Roberto Bautista Agut of Spain 5-7, 6-4, 7-6 (3) on Saturday in the Garanti Koza Sofia Open in Sofia, Bulgaria.
Goffin collected 12 aces and saved six of the 11 break points he faced to win in two hours, 44 minutes.
"It was a tough match, tough battle," said Goffin, who will face Grigor Dimitrov of Bulgaria in the final on Sunday. "I knew before that I had to fight against him because he's such a great fighter. I knew at the end I had to be offensive."
The 26-year-old Goffin fell behind 3-1, but came back in a third set that featured six service breaks to beat Bautista Agut for the first time in three tries.
Goffin will try for his third career title and his first since 2014 against Dimitrov, who needed only 64 minutes to defeat Nikoloz Basilashvili of Georgia 6-1, 6-3.
Dimitrov, the home favorite who is bidding for this second title of the season, won 89 percent of his first-serve points and saved all three break points he faced.
Dimitrov beat Kei Nishikori of Japan last month to win the Brisbane International, and has a 2-0 record against Goffin, including a 6-3, 6-2-, 6-4 quarterfinal victory last month in the Australian Open.