The Filipino-born 21-year-old whipped the home crowd into a frenzy with a 6-4 6-3 6-4 victory over Spain's Martin Landaluce in the first round of Australian Open on Monday.
Rugby league and union dual international Sonny Bill Williams was among the fired-up faithful, sitting in the Sydneysider's box.
McCabe said the New Zealand legend was like a brother to him and had imparted plenty of words of wisdom.
"I've known Sonny every since I was a kid," he said post-match.
"We're really close. We're family friends.
"Sonny's amazing. Sonny being Sonny, he has all of the experience being one of the best players ever to step on the field."
It was McCabe's first ATP Tour-level victory and first win at a major after making his Open main draw debut last year and two previous losses in qualifying.
"I've lost, I think, three or four now in a row," McCabe said.
"So just to get that monkey off my shoulder, I'm just happy."
McCabe's path to the top of tennis has been anything but typical.
He was born in the Philippines and relocated with his family to the Sydney suburb of Rockdale when two months old.
The apartment complex where he lived had a swimming pool and a tennis court, where his father handed him a racquet as a two-year-old and had him rallying within months.
But it was his swimming talent that earned McCabe a scholarship to a private school, where he also picked up the flute from scratch after learning the piano.
His life was gruelling during those years, with swimming, orchestra, school and homework keeping him busy on most days from 4am to late at night.
"Childhood was quite tough," he said with a smile.
"But I got through it and I think that it definitely builds character and builds strength."
McCabe dropped tennis for the scholarship at age 10 and didn't pick up a racquet to compete again until he was 15, and then only began touring after finishing high school.
"The last two years have just been a learning experience," he said.
"There's a bit of inexperience but I think now I'm better at handling a lot of things and going through certain situations."
His second-round opponent is Alex Michelsen, who stunned 2023 Open finalist and 11th seed Stefanos Tsitsipas in four sets earlier in the day.
McCabe had to be content with taking a set off the American world No.42 in his main draw debut in Melbourne last year. He is keen to exorcise his demons.
"I try not to remember that match," he said.
"It's going to be a battle. I'm looking forward to it."
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