Roger Federer and Felix Mantilla each won Saturday to reach the final of the Italian Open.
Federer advanced when Juan Carlos Ferrero retired in the second set because of an arm injury, while Mantilla had to rally past Yevgeny Kafelnikov 4-6, 7-6 (3), 6-4.
The fourth-seeded Federer was leading 6-2, 4-2 (30-0) when Ferrero shyly waved his hand to signal "enough."
Ferrero came into the match having won 21 of 22 clay-court matches this season, including titles in Monte Carlo last month and Valencia last weekend.
He said he would not miss the French Open, which starts May 26.
"It's nothing serious, but it's hurting," Ferrero said. "I've been playing a lot of matches in a row. Maybe I need some rest. I'm going to stop until the French Open."
Federer, who extended his leading match victory total this season to 36, was in complete control before the match was stopped short. He broke Ferrero's serve midway through the first set to go up 3-1 and then closed out the opening set with another break when Ferrero's weak forehand stopped before the net.
The match began to unravel with the Swiss player leading 3-2 and up 40-30 on the Spaniard's serve in the second set.
In Sunday's final, Federer will be aiming for his fourth title of the year and second in two weeks after capturing the trophy in Munich last weekend.