STILIYAN PETROV has backed James McCarthy to show his class for Celtic after a difficult full debut for the midfielder against Livingston.

McCarthy was one of several Celtic players who was produced seriously below-par performances as Ange Postecoglou’s side suffered a third Premiership away defeat of the season at the Tony Macaroni Arena on Sunday.

But Petrov believes that McCarthy will show the ability that once made him a regular performer in the English Premier League once he is up to full fitness.

“It’s very difficult for any player coming in who hasn’t played in a long time,” Petrov said. “You need to be at full strength to it’s been hard for him to hit the ground running.

“It’s going to take him time to build his fitness. We know he’s a good player. He’s played a lot of games in the top league in England, so we know he’s got it.

“But in football these days you have to run. It’s difficult if you are not match fit, but I’m sure the team behind Ange are working hard to get him up to speed.”

The return of Callum McGregor to the midfield will be helpful to McCarthy on an individual level according to Petrov, as well as the Celtic team as a whole, and he is glad to hear that Postecoglou is looking to extend his captain’s contract.

“Callum has been instrumental at Celtic – and not just this season,” he said. “We’ve seen how much of a miss he is when he’s not there.

“He has really matured as a player, you can see he leads the boys in the right way since he took over from Scott Brown as captain.

“He is a huge miss because he’s also one of the players who makes a difference in the big games.

“You can understand why Ange wants him to sign a new contract. Everyone wants to keep their best players –and he is one of the top guys. I really hope they can keep him for the long term.

“I know there has been talk about England for a while but at this moment I think he understands his responsibility to lead this Celtic team.

“The club are going through a transition and they need someone who has been here a long time and understands the club.

“Callum is taking this role very seriously and I hope it continues.”

*Stiliyan Petrov was speaking at The John Hartson Foundation Golf Day at Turnberry. The Hartson Foundation supports various cancer charities around the UK.