Andy Murray saved two match points before winning an epic encounter with Frances Tiafoe at the European Open in Antwerp.
The former world number one emerged triumphant from a gruelling contest lasting three hours and 45 minutes, the longest three-set match of the 2021 ATP season.
Having warded off two match points in the decisive tie-break, Murray clinched a 7-6 (7-2) 6-7 (7-9) 7-6 (10-8) victory with a drop shot that landed just out of Tiafoe's reach.
"I think that's the first time in my career I've played a 7-6, 6-7, 7-6 [match]. I don't think I've ever played a match like that," said Murray, who next faces second seed Diego Schwartzman. "I think it's the longest three-set match I've played by quite a distance. I'm tired right now, obviously it was an unbelievable battle.
"Nowadays obviously my body is old now. I've played a lot of matches on the tour. I don't mind playing long matches, but that was taking it to another level.
"Brilliant match, amazing atmosphere, thanks to everyone who came and supported. It's just so nice to be back and playing in front of crowds again."
American prospect Jenson Brooksby left his compatriot Reilly Opelka flummoxed as the fifth seed was beaten 6-4 6-4.
Opelka was heard proclaiming Brooksby was the "best player I've played in my whole life" during the second set as he struggled to interpret the 20-year-old's service game. Brooksby will face Botic van de Zandschulp in the next round.
There was another upset when sixth seed Alex de Minaur lost 6-4 6-0 to Brandon Nakashima, who has twice reached ATP-level finals this year and will next face Henri Laaksonen, victorious over Benoit Paire.
Lorenzo Musetti needed two tie-breaks to defeat fellow Italian Gianluca Mager, while Alejandro Davidovich Fokina – quarter-finalist at the French Open this year – eased past Jordan Thompson 6-3 6-3.
Respect, @andy_murray @FTiafoe— ATP Tour (@atptour) October 19, 2021
: @TennisTV | #EuropeanOpen pic.twitter.com/QW1F4L0Akf
At the Kremlin Cup, fifth seed Alexander Bublik suffered a surprise straight-sets defeat to Illya Marchenko, the world number 164 winning by a 6-4 6-3 scoreline.
Adrian Mannarino battled through against wildcard Roman Safiullin, but Laslo Djere lost in three sets to Gilles Simon.
Ricardas Berankis and Egor Gerasimov also progressed, while Guido Pella retired from his match with Pedro Martinez.