Daniil Medvedev beat Alexander Zverev to book a spot in the quarter-finals, while world number one Novak Djokovic was stunned by Lorenzo Musetti on Thursday in the third round of Monte Carlo Masters.
Djokovic's quest for a record-extending 39th Masters trophy was prolonged on Thursday after falling to a 4-6, 7-5, 6-4 defeat at the hands of Musetti.
Djokovic's last meeting with the Italian on clay was a gruelling Roland Garros clash in 2021, in which he battled back from two sets down to win, but this time it was Musetti that claimed a comeback victory in windy conditions.
Both players struggled on their serve in a contest littered with 15 breaks of serve, but Djokovic appeared to have the match in hand as he comfortably took the first set.
However, Musetti refused to go down without a fight and the Italian stepped on the gas in the second set to level the topsy-turvy encounter.
Not even a lengthy halt in play due to rain could dampen Musetti's momentum, and the 21-year-old once again took advantage of a weak serving performance from Djokovic to break and take the win.
"I'm struggling not to cry. It was a really long match, not easy conditions. It was a bit windy, cold," Musetti said. "I'm really proud of myself. The rallies were long, it was a tough, physical battle. Beating Novak is something remarkable for me."
Musetti will next face fellow Italian Jannik Sinner, who beat Hubert Hurkacz.
In the last act of the evening, Medvedev continued his impressive form this season with a 3-6, 7-5, 7-6(7) thrilling win over Zverev in the 14th chapter of their long-running rivalry.
A month after defeating Zverev in the last 16 at Indian Wells, the winner of four hardcourt titles this year recovered from a set down to beat the German once again in what was his first clay clash.
After winning the first set, Zverev was 5-4 serving for the match in the second when Medvedev earned a crucial break and won three straight games to force a decider.
The 27-year-old Russian claimed his 31st win of 2023 after saving two matchpoints in a dramatic tiebreak.
"That was a crazy match," said Medvedev. "He served two times for the match, but that is also clay courts. You can come back at any moment.
"The serve doesn't count as much, so as soon as someone gets a little bit tight, the match can turn around in one second. That's what I managed to do."
Seventh seed Sinner was made to toil by Hurkacz in a 3-6, 7-6(6), 6-1 win.
Watched on by sprint great Usain Bolt, Sinner saved a matchpoint in a second-set tiebreak and held firm in a decider to complete the win as Hurkacz faded.
Defending champion Stefanos Tsitsipas eased past Nicolas Jarry in just over 90 minutes, saving two break points to claim a 6-3, 6-4 victory and extend his winning streak at the tournament to 12 matches.
Russian Andrey Rublev beat compatriot Karen Khachanov 7-6(4), 6-2, while American Taylor Fritz dispatched Jiri Lehecka in three sets.
German qualifier Jan-Lennard Struff stunned fourth seed Casper Ruud 6-1, 7-6(6), ending the Estoril champion's nine-match winning streak on clay stretching back to last July.
Italian Matteo Berrettini earlier withdrew from his meeting with sixth seed Holger Rune due to an abdominal injury, sending the Danish teenager through to the last eight.
