Italian Lorenzo Musetti beat Stefanos Tsitsipas 1-6, 6-3, 6-4 on Friday to knock out the holder and reach the semifinals of the Monte Carlo Masters.
Musetti, 23, fought back after losing the first set against the three-time tournament winner to tee up a last four tie with Australian Alex de Minaur.
Earlier, De Minaur produced a ruthless performance to dismantle an out-of-sorts Grigor Dimitrov 6-0, 6-0 in just 45 minutes, with the match finishing to a backdrop of boos from the crowd.
Dimitrov mustered just one winner in total, made 23 unforced errors and won only five points in the second set.
Carlos Alcaraz battled back from a set down to beat French rising star Arthur Fils in a gripping quarterfinal.
The four-time Grand Slam champion, targeting his first Masters title since winning in Indian Wells last year, saved three break points in the 11th game of the second set en route to a dramatic 4-6, 7-5, 6-3 victory.
"I think his level is high right now and he puts a lot of pressure on his opponents," Alcaraz said of his beaten opponent.
"Today I could feel it but in some moments he just made a few mistakes and I tried to make the most of those points and wait for my chances."
He will face unseeded fellow Spaniard Alejandro Davidovich Fokina on Saturday for a place in the final.
Alcaraz's only title this season remains the ATP 500 event in Rotterdam in February but he appears to be enjoying his return to clay.
The 20-year-old Fils, seeded 12th, suffered a third successive quarterfinal loss at Masters events this season after going out in the last eight at Indian Wells and the Miami Open.
Alcaraz is a strong favourite to lift the title after early exits for Novak Djokovic and Alexander Zverev, at an event where he had lost his only previous match in 2022.
He showed all of his battling qualities to get the better of Fils, in what is likely to have been their first meeting of many.
Earlier, Davidovich Fokina cruised into the semifinals with a dominant victory over Alexei Popyrin.
World number 42 Davidovich Fokina, who was runner-up at the tournament in 2022 to Stefanos Tsitsipas, swatted aside Australia's Popyrin 6-3, 6-2 in the last eight.
Davidovich Fokina was full of confidence after dumping out British fifth seed Jack Draper in the last 16 and put on another accomplished display.