Vasilis Barkas' self-belief is sure to be tested at Celtic, according to former Hoops keeper Craig Gordon.

The Greece international has come under scrutiny since signing from AEK Athens in July on a four-year deal for a reported fee of £5million and there were questions asked about the first goal he conceded in the 2-0 defeat by Rangers at Parkhead on Saturday.

Gordon, who returned to Hearts for a second spell in the summer after six years at Celtic, believes the mental aspect of playing for the Glasgow giants is crucial.

The 37-year-old, speaking at the relaunch of the McDonald's Fun Football programme which will see the company provide over five million hours of free football to five to 11-year-olds by 2022, told the PA news agency.

"Trying to block out all the noise, that is part of the mentality, to carry on regardless, to do what you do well.

"There is always going to be so much scrutiny, so much online, everyone is going to have an opinion and it is very difficult to shut that out.

"You may not look at social media but one of your friends will text you what has been said and you see it anyway. It is very difficult to stay clear of all that stuff and not let it affect you.

"You have to have a great belief in yourself and your own ability to go out there and perform in what is a very pressurised situation.

"Overall I dealt with it fairly well but at times it does get very difficult. It is all about working hard in training and making sure you are ready for the games.

"There is no magic wand, no real piece of advice to help anyone with that.

"It is a very difficult place to be, such a pressurised job, especially at Rangers and Celtic where you only get one or two big actions to do in a match.

"It is something that takes a bit of getting used to so there are no real words of advice but I am sure he will come good."

:: Hearts and Scotland goalkeeper Craig Gordon was relaunching McDonald's Fun Football programme,  which offers fun, free and safe football sessions for children age 5-11. Find your nearest Fun Football Centre and to sign up for a session at: www.mcdonalds.co.uk/funfootball.