McCarthy broke his leg during the last quarter of WA's final game at the NAB AFL Under-18 Championships in early July.
The injury sidelined the 18-year-old for the remainder of the season, but he refused to let it get him down.
"Mentally, at the start, it was really annoying. I hate not being able to run," he told AFL.com.au during the draft combine at Etihad Stadium.
"But after I got over the little hump and started running again in early September, everything was fine."
Still, the broken leg did interrupt what was promising to be a great year for the laconic youngster, whose trademarks are his mop of shaggy hair and penchant for wearing a headband.
Prior to suffering the injury, he was one of the standout performers at the national championships, booting 12 goals and winning All Australian honours.
"I was playing good footy, things were falling into place for me and my confidence was up, so it was a setback, a big setback," McCarthy said.
"And I missed the WAFL finals with the South Fremantle colts, so that really hurt a lot."
These days McCarthy stands 193cm tall and is rated the second-best key forward behind Tom Boyd in the draft pool.
"He's an explosive tall forward with excellent leg-speed and overhead marking ability," is the summation of AFL talent manager Kevin Sheehan."
Early in his junior career, when he was playing alongside close mate and fellow draft prospect Dylan May, McCarthy wasn't always destined to become a key position player.
"Back in the under-14s and under-15s I was a smaller player, out on the wing or in the forward pocket," he said.
"But I had a big growth spurt though the under-16s and under-17s, and I've ended up playing as a tall forward."
A passionate Fremantle supporter who has been compared to Dockers star Nat Fyfe, McCarthy is from a family that has a long connection to Australian football.
"My grandad played footy in Tasmania back in the day, and he was pretty good at it," he explained.
"And my dad wasn't too bad himself, so I suppose that's carried through to me."
However, McCarthy also showed plenty of promise as a cricketer and was part of Western Australia's under-17 squad last year.
"At a younger age I was probably pushing towards cricket," he said. "I was probably better at that.
"I was an opening batsman. I started off as a bowler at a young age, but they kept coming out slower and slower every year, so I went to batting and wasn't too bad at it.
"But with the growth spurt I started to focus more on footy."
Due to his leg injury, McCarthy was unable to do the physical testing at the combine, but he still came to Melbourne for the event and spoke to a number of clubs.
"I had a few interviews here and there, but they all seemed to say the same things and ask the same questions," he said.
"So I didn't really get an idea who was keen on me or not.
"They all asked me how my leg was going. I showed them the x-rays and the doctor's report, and they all seemed to be happy with the way it's recovering."
McCarthy is tipped to be a first-round selection when the NAB AFL Draft takes place on November 21.
He is a sneaky chance to remain in WA next year, with his beloved Dockers in the market for forwards.
But the odds are that he will probably find himself moving interstate after the draft in late November.
"It would be hard to leave home, but if you get the opportunity you've got to grab it with both hands and take it no matter what," he said.
"If I get picked up I'll be proud as punch."
Twitter: @AFL_AdamMcNicol
