Foot and back problems have limited the 20-year-old South Australian, who was selected with pick 66 in the 2011 NAB AFL Draft, to just three AFL games.
But the Cats recently handed him a new two-year contract.
"(I'm) really happy about that," McCarthy told K-Rock radio on Saturday night.
"It obviously makes you feel more secure at the club, and I think it just helps you mentally relax and work on what you really need to work on, and move forward without that stress of (wondering if) you’re going to be here next year or not.
"When I finally did sign the contract, I said to 'Balmey' (football manager Neil Balme), 'Wellsy’ (recruiting boss Stephen Wells) and 'Scotty' (head coach Chris Scott), 'Thanks for keeping me on'."
From Bordertown via SANFL club Glenelg, McCarthy, whose bubbly personality has made him a popular figure at the Cattery, made his AFL debut against Greater Western Sydney midway through the 2012 season.
But he was diagnosed with a hot spot in his foot a short time later, and the injury lingered for 12 months.
Although he didn't play a game at any level in 2013, McCarthy finally shook off his foot problem during the latter stages of last season.
That enabled him to train with the senior team during the last two weeks of its home and away campaign and then during the finals.
After a big pre-season, McCarthy was selected for Geelong's round one clash with Adelaide.
He then lined up against the Brisbane Lions in round two, before being struck down by a back injury.
As McCarthy admitted on Saturday, he initially believed it was only a short-term problem, "but it turned out it was a bit worse than I thought and that put me out for 12 weeks".
He returned to the field in late June and has now played five VFL games, including an outstanding performance against Sandringham on July 20, in which he booted four goals.
Twitter: @AFL_AdamMcNicol
