After six years at Merseyside, during which he made 133 appearances for Everton, the 29-year-old left the club last summer to sign for Crystal Palace.
While at Goodison, McCarthy suffered from a number of hamstring problems before returning to the side under Sam Allardyce.
He was even more unlucky after breaking his leg in an abnormal collision with Salomon Rondon against West Brom in January 2018.
“It got me back to square one,” McCarthy told Sky Sports.
“It was mentally difficult, to be honest, just trying to figure out how long it was going to last. ”
One Everton player who is also used to dealing with long-term injuries is Seamus Coleman, whom McCarthy played alongside the Blues and the Republic of Ireland National Team.
McCarthy praised Coleman and the Everton kiosks for helping him manage the recovery.
Everton FC essential news
“Seamie has always been there for me from the minute it happened,” added McCarthy.
“He showed me videos of the kind of work he did during his recovery, and the kiosks in Everton were also brilliant.
“The road has been long, but as you get closer to recovery, you feel more confident with your leg.
“First you go back to the gymnasium, then before you know it, you’re back on the grass. “
Marco Silva replaced Allardyce in 2018, and McCarthy admitted that despite a good start, he was ultimately frustrated at being kicked out of the team.
“Everything was good at the start,” says McCarthy. “He was telling me to get back in shape and that we would look into it after I got back to training.
“Personally, I felt good. I felt like I had worked hard to recover from the broken leg and I trained daily with the team. But then it would happen on weekends and I would not play.
“It was frustrating. You train all week to make sure you’re in good shape and looking forward to the game. But at that time, it just didn’t happen to me.
“Marco had brought his own players and I respect that. Managers want to bring their own players. But unfortunately, that meant I was not playing. ”