While de Minaur enjoyed a walkover on Wednesday after his second-round opponent Alexander Blockx was injured in practice, his potential third-round adversaries had to slog it out in what Mensik described as "insane conditions" for four hours 41 minutes.
The Czech 26th seed ended up victorious but stricken on his back, unable to pick himself off the clay on Court No.6 for several minutes amid alarming scenes after battling to a 6-3 2-6 6-4 1-6 7-6 (13-11) victory over Argentine Mariano Navone.
Somehow, Mensik, cramping up before serving the final point, managed to hit the winning forehand before dropping to the clay.
Medical staff put ice towels around his neck and chest and an ice pack on his forehead before helping him to his feet, but he'd taken just a few steps towards the locker room when he was placed in a wheelchair.
This was less than 48 hours before he's due to play de Minaur, one of the fittest, fastest players on the circuit who delights in making it a physical trial.
But Mensik, the last man to beat world No.1 Jannik Sinner in February, insisted later he would be ready for the third-round duel on Friday.
"Even if it looked horrible at the end, after 30 minutes in the locker rooms, when I was out of the sun, I started to feel much better. I'm here, feeling pretty well," he told reporters later, admitting his "body just turned off".
Mensik said he'd had an ice bath and done some recovery work in the gym after the match.
"I would say I'm feeling pretty well - it's just now about to put back the strength, a lot of fluids, and I'll be OK,'' he said.
"Alex has something similar game style as Navone today, so, of course, it will be very, very difficult to put him under the pressure, but I'm doing pretty well here, feeling really in good form, so I will do my best to keep fighting and to get the W."
But Mensik was fuming about the ordeal in the heat.
"It's insane to play in this weather, and especially in front of the sun,'' he said. "To be there for more than four and a half hours, that's just insane.
"Even with the breaks, you don't have that much time. You have just one minute, which when you sit it's already just 30 seconds. There is not that much time to cool yourself down."
All of which potentially spells good news for de Minaur, who's only needed three sets so far against British qualifier Toby Samuel and is just a win away from a place in the last 16.
