Rome: Eight-time champion Rafael Nadal came through 6-4, 6-0 against compatriot Fernando Verdasco to set up a rematch with Greek rising star Stefanos Tsitsipas for a place in the Italian Open final.
Tsitsipas advanced after Roger Federer " returning to clay after a two-year absence " retired with a right leg injury before their game.
The 32-year-old Nadal, seeded second, advanced to his fourth straight semi-final but has not managed to go further on clay this season, ahead of his bid for a 12th French Open title at Roland Garros, starting on 26 May.
Tsitsipas beat Nadal in last week's Madrid Open semi-finals before falling to Novak Djokovic, but lost to the Spaniard in the Australian Open semis earlier this year.
Reigning US and Australian Open champion Naomi Osaka had earlier said she could not compete because of a problem with her hand. The Japanese star was due to meet Madrid Open champion and sixth seed Kiki Bertens. Bertens goes through to meet either Britain's Johanna Konta or Czech Marketa Vondrousova.
On court, Argentina's Diego Schwartzman dispatched Japanese sixth seed Kei Nishikori to reach the semi-finals.
Schwartzman, 26, won 6-4, 6-2 in 87 minutes in the quarter-final for his first win in four meetings with former US Open finalist Nishikori.
The world number 24, a French Open quarter-finalist last year, has not dropped a set so far on the red clay of the Foro Italico and next faces either the top-ranked Djokovic or compatriot Juan Martin del Potro.
"It's not the best result I wanted, but I'm getting better every tournament from Barcelona and looking forward to playing the French," said Nishikori.