The former England international surprised all by signing a lucrative five-year contract with ambitious League Two outfit Notts County, but quit after just one game.
"I wasn't in for Sol," McCarthy told Sky Sports News. "I got asked.
"Maybe travelling to Morecambe and getting beat 2-1 it was a reality check. I'm not being detrimental to Morecambe.
"I'm saying playing in that league coming from the illustrious career that he's had and then going to Morecambe was a shock.
"You play against two young lads who are chasing it in corners and running around and banging it into you and knocking it about.
"That's the sobering effect, playing against those players."