That’s according to former Hoops hitman Frank McAvennie, speaking exclusively to Football Insider as the midfielder missed his side’s last three games.
McCarthy, 30, has only made eight appearances for Celtic since joining the club in the summer as he picked up various knocks.
As quoted by The Scotsman (19 October) Ange Postecoglou claimed the summer signing will be available for the visit of St Johnstone at the weekend.
McAvennie still rates McCarthy and told Celtic to be careful with him as he could be a vital player at Parkhead.
“He’s a big problem,” McAvennie told Football Insider correspondent Ben Wild.
“He is the one Celtic wanted to come in and sit in the middle. That’s an important part of that side.
“It’s not happening because he’s not fit enough. He’s getting more injuries because he’s not fit enough when he does play.
“I don’t know what the situation is, I like him. Turnbull and Rogic are great going forward.
“So we need someone to sit in the midfield and win tackles. That’s what he’s for and he is a good player.
“I don’t think there is anyone else at Celtic who can do that, so we need to be careful with him.”
Celtic have won all three games McCarthy missed with his latest knock.
The Hoops beat Ferencvaros at Parkhead after back to back away wins against Motherwell and Aberdeen.
This article was originally posted here