Top seed Grigor Dimitrov reached the Nastase Tiriac Trophy final after Frenchman Gael Monfils retired from their semi-final with an ankle injury.
Monfils twisted his right ankle when walking onto court in Bucharest and quit at 5-1 down after just 16 minutes.
Dimitrov, 22, will next face defending champion Lukas Rosol after the Czech beat Dutchman Robin Haase 3-6 6-3 6-2.
Jamie Murray and John Peers lost to top seeds Jean-Julien Rojer and Horia Tecau in the doubles semi-finals.
The British-Australian partnership, seeded fourth, went down 2-6 7-6 (7-3) 10-8 in one hour and 35 minutes.
Monfils, who withdrew from the Casablanca Open with an ankle injury earlier in the month, revealed that he had rolled his ankle, and after winning his first service game he was clearly feeling discomfort.
Bulgaria's Dimitrov will head into Sunday's final looking to win his third ATP title and second of 2014.
"It is disappointing for Gael," said Dimitrov. "As much as I am happy, it is an undeserved win and unfortunately it had to end that way.
"I saw what happened. I hope he will be OK for the coming weeks."
At the Barcelona Open, Spain's Nicolas Almagro could not build on his quarter-final winner over Rafael Nadal as he went down 7-5 6-3 to Colombian Santiago Giraldo.
Fourth seed Kei Nishikori of Japan beat Latvia's Ernests Gulbis 6-2 6-4 in the other semi-final.