Top seed Daniil Medvedev crashed out of the BNP Paribas Open in Indian Wells after a three-set defeat to Grigor Dimitrov.
The Bulgarian staged a spectacular fightback from a set and a double-break down to triumph 4-6, 6-4, 6-3 as the newly-crowned US Open champion’s game collapsed.
Medvedev had been in dominant form since his breakthrough win at Flushing Meadows and nothing looked set to change as he took the first set and stormed into a 4-1 lead in the second.
But inexplicably the Russian lost his range and Dimitrov reeled off eight games in succession to not only level the match but to establish a strong advantage in the decider.
The Bulgarian duly served out to love to complete one of the biggest wins of his career and seal his place in the quarter-finals.
Dimitrov was joined by Britain’s Cameron Norrie who reached the last eight of a Masters 1000 event for the first time after defeating Tommy Paul.
The British No 2 overcame the American in three sets, reaching the last eight with a 6-4, 4-6, 6-2 victory.
Norrie broke serve early on in the first set before a string of errors from Paul gifted his opponent a second successive break of serve.
Norrie surged into a 4-1 lead but Paul got a break back to move within one game of the Briton, who held his nerve to serve out the set.
An exchange of breaks in the second set saw it go down to the wire before being decided by the American breaking serve in the 10th game to take the set and level up the match.
There were also early breaks of serve each in the deciding set before Norrie surged clear to take the win, moving him to within one more victory of replacing Dan Evans as the British number one.
Diego Schwartzman is also through to the quarter-finals after a 6-3, 6-3 win against Casper Rudd, while there was also a straight-sets victory for Hubert Hurkacz who overcame Aslan Karatsev 6-1, 6-3.
Second seed Stefanos Tsitsipas was troubled initially by Alex de Minaur before defeating the Australian 6-7, 7-6, 6-2, with the Greek next facing Nikoloz Basilashvili following the Georgian’s straight-sets upset of 24th seed Karen Khachanov.
And American Taylor Fritz will play third seed Alexander Zverev after respective victories against Jannik Sinner and Gael Monfils.
Dual champion Victoria Azarenka of Belarus is through to her fourth semi-final at the BNP Paribas Open following a straight-sets win over the 19th-seeded Jessica Pegula.
The 27th seed, who won the tournament in 2012 and 2016, sent down 21 winners to her American opponent’s 18 unforced errors to emerge a 6-4, 6-2 victor in one hour and 34 minutes.
Azarenka will next face Jelena Ostapenko after the Latvian battled back from the brink of defeat against unseeded Shelby Rogers of the US.
The 2017 French Open champion had a furious start as she won five of the first six games in just 22 minutes before she found her second serve under pressure in the second set.
Both players missed opportunities in the final set, with Ostapenko closing it out by winning the final four games and the match 6-4, 4-6, 6-3.