Scotland forward Steven Naismith will have no problem renewing his rivalry with new-found friend Aiden McGeady when the latter lines up for the Republic of Ireland on Friday night.

McGeady's return to Celtic Park is one of the intriguing aspects of the Euro 2016 qualifier. The former Hoops player lined up against Naismith in Old Firm derbies but their rivalry stretches back even further to the days when the players, both of whom are 28, faced each other in boys' football.

Both players' will to win makes them spiky characters on the pitch - Naismith is not shy of moaning to referees and opponents while McGeady once had a physical disagreement with Celtic team-mate Neil Lennon on the park.

But Naismith's character off the pitch could not be more pleasant - he spent lunchtime today promoting an initiative in Glasgow that helps injured war veterans return to civilian life and employment.

Naismith and McGeady have struck up a friendship off the park after they teamed up at Everton earlier this year, but they will revert to being fierce opponents on Friday.

Naismith said: "We have renewed that for the last year when we spoke about old times when we have played against each other, and in training as well.

"It will just be another one to add to the collection of bragging rights.

"Even guys that I have probably not played much against, they have an idea of what you are meant to be like and they form an opinion.

"Over time, when you become friends, that opinion changes a lot. I have certainly done it with players.

"But it's the usual, when you go out on the park you want to win more than anything else. You know the feeling of playing for Scotland and you dream about it as a kid and you have the opportunity to do it.

"All the friendship goes out the window until the end of the game.

"But he's a top-quality player and someone we will need to watch. Even for Everton, he maybe started a bit slow but over the past month he has probably played his best football for Everton. He will be a threat."

Naismith has told Scotland fans to expect a more astute player than the McGeady that left Celtic for Spartak Moscow in 2010.

"I think he has matured a lot," Naismith said. "Like a lot of young forward players they try to do everything themselves, but over time, as you get older, you understand that teams might double up on you so there's a free person that can do a bit more damage and you become more of a team player.

"From seeing him from afar to becoming a team-mate, I think that's the biggest change."

While Naismith is happy to put aside his friendship with McGeady for 90 minutes, there will be more than 50,000 Scots at Parkhead who may be even less welcoming.

Paisley-born McGeady is expected to get a hostile reception along with his fellow native Scot and club and international team-mate James McCarthy, although the former Hamilton midfielder is struggling with a hamstring problem.

But Naismith thinks too much is being made over the issue.

"The fans are going to come and support Scotland, and that's going to be their main priority," he said. "Every away ground I go to fans boo me, and I shout comments. It's part of the game.

"I don't think it will be that big a deal, I don't think it will be something that will play on their minds or even the Scotland fans'. They will hopefully be cheering us.

"We've not really mentioned anything about that. For Aiden personally it's going to be a big event going back to Celtic Park."

Naismith was hosting a reception for construction firm City Building, Glasgow Housing Association, Royal Strathclyde Blindcraft Industries and Helping Heroes, a partnership that he has helped for several years.

The former Rangers player vowed to do something for war veterans after striking up a friendship with a soldier who wrote to him from Afghanistan with words of encouragement after he suffered a serious knee injury.

"I thought about what to do to help these guys or raise awareness to make their lives that wee bit easier," Naismith said.

"They have risked and given so much for others. I feel strongly that it is our turn to give back in recognition and support."