World number one Donald improved upon his overnight four-under par score with six further birdies to move to within four shots of outright leader Alvaro Quiros, whereas McIlroy’s challenge again faltered badly.
A bogey and a double bogey on the front nine, at the third and seventh holes respectively, saw the Northern Irishman slip down to four under before four birdies thereafter saw him rally back up to eight under.
Donald ended the day in fourth place and well inside his top-nine requirement, while McIlroy — who needs to win here — finished up tied for eighth.
However, despite the eventual outcome looking little more than a foregone conclusion barring something of a minor miracle at this stage, Donald understandably remains somewhat wary of a late sting in the tail.
“You cannot take anything for granted in this game,” the 34-year-old, who is chasing a winning double on both the European Tour and US PGA money lists, said. “I would be foolish to expect that it’s all over.
“Sunday will be just like any other day in so much as my focus will be on trying to catch whoever is the leader and win the tournament.
“I’m going to try and treat Sunday’s round like the fourth round of any other tournament.
“I’ve said from the start that I could get in trouble if I concentrate on that ninth position.”
Donald’s quest for a seismic slice of sporting history has been hampered somewhat by the pressure of the situation and he has likened his predicament to being at Q-School again.
“In a certain way, it’s almost felt a little bit like Q-School,” he added. “I haven’t been there for 10 years, but – after doing all the great work that I’ve done this year – if I wasn’t able to quite complete it, I feel like I’d walk away with missing out.
“It’s going to be a tough day on Sunday. I’m going to feel it, but I’m in a good position.”
It’s an advantageous placing that McIlroy doesn’t believe he’ll be able to overturn too, with the 22-year-old conceding defeat in this attempt to catch and conqueror his adversary.