Stefanos Tsitsipas advanced to the last-four in Monte Carlo on Friday when his quarter-final opponent Alejandro Davidovich withdrew after losing the first set as 11-time champion Rafael Nadal sets his sights on reaching his 75th Masters semi-final.
Tsitsipas, the world number five, will play his sixth Masters 1000 semi-final on Saturday, and his first in the principality, against Englishman Dan Evans, who battled past Belgian David Goffin 5-7, 6-3, 6-4.
Struggling with an injury to his left thigh, Spaniard Davidovich tried an underarm serve when facing set point. Tsitsipas pounced to hit a winning backhand return with his opponent quitting after dropping the opener 7-5.
Until he was hurt, world number 58 Davidovich gave his Greek opponent problems.
But at 3-3, Davidovich called for the doctor to treat his left thigh. He immediately managed the first break of the match, as Tsitsipas began to show signs of irritation, to the point of receiving a warning for swearing.
"The level of play was high at the beginning," said Tsitsipas. "We played a lot of long rallies, and the intensity was high in every one of them."
Tsitsipas immediately broke back and as Davidovich struggled, broke again to end the set and the match.
"I noticed he was hurt. His leg was hurting. But I didn't want to think about it, I tried to pretend he wasn't injured and keep playing as I was doing," said Tsitsipas. but he added: "I had to do what I had to do: force him to run and work on every point. At the end of the day, he wasn't able to play me until the end."
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Evans, who stunned world number one Novak Djokovic in the previous round, edged Goffin after the Belgian made 47 unforced errors, including a final forehand on match point, to win.
Goffin also only converted two of the 17 break points. Evans was not very effective either, but he did win four of the nine break points.
The 30-year-old Briton, who was playing in his first Masters 1000 quarter-final on a clay court that is not his favourite surface.
"I played good today. I felt a bit more pressure to not just win yesterday and give a bad performance today," said Evans.
"It wasn't easy after the match yesterday, I felt really tired afterwards. To get back and focus, it was difficult. I am proud of how I came back."
Defending champion Fabio Fognini was knocked out Norway's Casper Ruud who goes on to face either Nadal or Andrey Rublev for a place in the final.
Nadal has a 2-0 career edge over the eighth-ranked Russian who has never taken a set off the Spaniard.
Victory for 20-time Grand Slam title winner Nadal will put him into his 75th Masters semi-final and two wins away from a 36th title at this level.
Unseeded Ruud, ranked 27, won 6-4, 6-3 against the 15th seeded Italian who hit 33 unforced errors.
Ruud, 22, makes the last four 24 years after his father Christian had also reached the quarter-finals at the tournament.
"He can be very surprising. He can make winning points from anywhere on the court," said Ruud.
"So I'm happy to have remained focussed. We've both played better tennis in our lives, but in the end I managed to put in a few more balls than him and got the upper hand on key points."