On Tuesday, Marin Cilic, the 2014 US Open champion, had caused his first shock at the UAE tournament by beating world No.8 Alex de Minaur in three sets.
Not content with that, the 36-year-old Croat re-emerged on Wednesday to end the last-16 hopes of Aussie No.2 Alexei Popyrin, coming from a set down to prevail 5-7 6-3 6-4.
On what proved a rather chastening day for the Australian challenge, the last man standing, Sydney's Chris O'Connell, who'd done well just to qualify, also got beaten later on 7-6 (7-2) 6-2 by Matteo Berrettini.
Popyrin had gone into his match, hoping for a confidence-boosting run at an ATP tournament after he'd failed to win a match in any of his first four events of an injury and illness-hit early-season campaign.
The world No.27 had accounted for Lebanese Hady Habib in his opening round and things looked to be going smoothly enough when he broke Cilic's delivery at the end of their first set to take early control.
But just as de Minaur had discovered 24 hours earlier, a rejuvenated Cilic, who's somehow producing some of his vintage best after years of debilitating injury struggles, is still a force to be reckoned with, his world ranking of 186 proving wholly illusory.
The Croat, who underwent knee surgery in May last year and returned four months later as the world No.777 to win the Hangzhou Open, becoming the lowest-ranked champion in ATP Tour history, continues to roll back the years.
Striking the ball with all his old power, he hit back in the second set against Popyrin, having survived a couple of break points at 2-2 and then breaking the big-serving Aussie in the sixth game.
Then in the decider, his serve was unchallenged throughout the stanza while he again relentlessly picked off Popyrin to break in the fifth game, which was to prove decisive.
It set Cilic up with a quarter-final against Canadian Felix Auger-Aliassime, who had earlier defeated Portugal's Nuno Borges 4-6 6-3 7-5.
Top seed Daniil Medvedev swore he didn't have a moment to even think about how to return Giovanni Mpetshi Perricard's monstrous serves - yet he still managed to come through this trial by aces 6-4 6-4.
"You don't have any time so it's pure reflexes and sometimes it makes life even easier because you don't think much," Medvedev admitted about his 21-year-old opponent's weapons.
"If you don't return it, you're not even disappointed! You just try to do your best - and I managed pretty well today."
Medvedev will next face Dutchman Tallon Griekspoor, who advanced by knocking out the defending champion Ugo Humbert 4-6 6-3 6-2.
