When he set his own record, Evans remembers feeling the nerves as he reached the 18th needing a par to eclipse the then standard set by future three-time major winner and Ryder Cup captain Padraig Harrington.
In contrast, as the pressure ramped up, O’Callaghan sensed McIlroy relished the attention.
The 36-year-old made headlines at Augusta this year for not addressing his final-round playing partner Bryson DeChambeau, but O’Callaghan saw the same singular focus even then.
“The more people that were there, you could see his focus go to the next level, he was now in his element,” he said.
“It wasn’t that he was showing off, but like he was going to entertain and really put on a show.
“He got into that zone or flow that people talk about and you could probably throw an orange at his head and he wouldn’t blink.”
If Evans felt McIlroy looked like a tour player that day, O’Callaghan remembers him celebrating one like too.
Five consecutive birdies to finish his round gave the watching crowd what they had hoped for with a monster putt on the 18th providing the exclamation point to the piece of history.
“It was one of those kind of moments that we were watching on TV at the time with Tiger Woods where as soon as the putt left the blade, you could just see this thing like a magnet to the hole, roll after roll after roll,” he said.
“Rory, you could see it in his eyes. He knows that he’s making it right off the bat, and he’s got the putter up and he’s ready to go with the fist pump, giving it the whole lot.
“It didn’t even touch the sides of the hole. Electric.”