This gifted musical and athletic allrounder has finally alighted on the sport as his chosen destination, with the late-starting but quickly-blooming 21-year-old virtuoso now ready to play all the right notes on his Wimbledon debut.
With his every progress being backed all the way by the great dual-code rugby legend Sonny Bill Williams, McCabe gazed over the All England Club and declared: "Definitely, tennis was the right choice.
"It's been my dream. When I was a kid, the first thing I did was pick up a racquet when I was two-and-a-half, and dad took me on the court and I could hit the ball, I could actually rally.
"Dad thought it was a bit silly, but he's got those videos somewhere, and I had a diaper on at the time!"
But McCabe, born in the Philippines to a Filipina mother and Irish father and a proud Sydneysider from the moment he moved to Australia with the family at six months old, had to wait a long time before he finally turned his attention to tennis three years ago.
Er, that's because he was just a bit too busy being one of life's achievers.
It was exhausting just listening to McCabe relating how during his school years in Sydney, after he got his swimming scholarship to Trinity Grammar, he would regularly get just a few hours sleep, fitting in all his early morning training in the pool with a bewildering amount of after-school musical fare.
"I was a flautist in orchestras and symphonic wind bands, marching bands and musicals, and played in the biggest venues in Sydney, like Town Hall and St Andrew's Cathedral and that was a big part of my life. And now it's tennis," explained McCabe, who's a fine choral soloist, guitarist and pianist.
Now he's on one of sport's greatest stages instead as the world No.181 after making huge progress over the last three years, culminating in his qualification for his maiden Wimbledon last week, which has set up his debut against Hungary's world No.58 Fabian Marozsan on Tuesday.
"When you're playing music and stuff, you're basically looking to be perfect, but in tennis, you can't be perfect," he shrugged, comparing his two worlds. "You're versing someone else, and they're doing everything that you basically don't want to do, that's the game. In tennis, you've got to take the punches, but also give them back."
Which brings us to Williams, the All Blacks great who's a long-time family friend and mentor to McCabe.
When McCabe came through qualifying last week, Sonny Bill sent him a message voicing his congratulations. "I'm very lucky and very grateful that I have him mentoring me and giving me all of his tips and advice, maybe the greatest of all-time in his field who carries himself so humbly."
Williams has got his own big sporting date lined up for next month, his boxing blockbuster in Sydney with rugby league hard man Paul Gallen. Asked for his prediction, McCabe smiled: "I guess I definitely have Sunny, he's always my number one."
But could McCabe, a national junior 200m butterfly champ before he turned his back on the swimming grind, turn out to be as brilliant a sporting allrounder as his hero?
"Everyone has their own path, and you gotta make the most out of what you can make of it," shrugged McCabe.
"And if you believe in your dream, anything's possible."
