Roger Federer and Naomi Osaka both pulled out of the Italian opening on Friday before their quarter-finals due to injuries just a week before the start of the French open.
The 37-year-old Federer – returning to clay after a two-year absence – retired with a straight leg injury before playing Greek eighth seed Stefanos Tsitsipas.
"I'm not 100 percent physically and after consulting my team, it was determined that I was not playing," Federer said.
Tsitsipas, a runner-up in last week's Madrid Open, will now play either defending champion Rafael Nadal or Fernando Verdasco for a place in the final.
Osaka – winner of the last two Grand Slams in the US Open and Australian Open – had previously said she couldn't compete because of a problem with her hand.
"I woke up this morning and I couldn't really move my thumb," the 21-year-old told a press conference.
"I can't move my hand. I can't move my thumb, and I'm not sure I can play my fight.
"I tried to practice and grabbed my racket and I just felt this pain every time I tried to move my hand in different directions."
The Japanese star was due to meet Madrid Open champion and sixth seed Kiki Bertens to a place in the last four in Rome.
Bertens goes through to meet either Britain's Johanna Konta or Czech Marketa Vondrousova.
"I haven't seen the doctor yet. I've seen physio," she said.
Osaka said she could stay in Rome before moving on to the French Open, but did not rule out competing in Roland Garros.
"I'll stay here one day and see how it is," she said.
"I haven't really talked to anyone, so don't really know the plan is yet. I've never had this problem before, it's completely new."
"I'll take it as if I went to Australia," added Osaka, who also retired with a leg injury against Bertens in the WTA final last October, before continuing to win the Australian Open.
"Grand Slams to me is like a playground, I have a lot of fun there."
– Top rank at Roland Garros –
Osaka won twice on Thursday after the previous day's game had been counted and held the world's number one place before heading to Paris.
Swiss 20-year-old Grand Slam winner Federer played in the Italian capital to prepare for his return to the French Open for the first time since 2015.
"I'm disappointed that I can't compete today," said Federer, who reached the quarterfinals in Madrid.
"Rome has always been one of my favorite cities to visit and I hope to be back next year."
Federer had been on trial almost four hours on Thursday, saving two fighters to win through three sets against Borna Coric after previous easing to a straight set winner over Portgual's Joao Sousa.
The former world number one had been a late addition to the Rome tournament when he sought clay court practice before his bid to add to his lone French open title in 2009.
In court, Argentine Diego Schwartzman sent Japanese sixth seed Kei Nishikori to become the first player through to the semi-finals.
Schwartzman, 26, won 6-4, 6-2 for 87 minutes in the quarterfinals for his first win against former US Open finalist Nishikori.
The 24-rank one-time French Open Quarter Finalist has not dropped a set so far at Foro Italico's red clay and next stands either over the world's number one Novak Djokovic or compatriot Juan Martin del Potro to a place in the finals.
? 2019 AFP