Gordon Strachan has always had a little bit of devilment in him, so it is little wonder that the Scotland manager appreciates such a quality in a player.

The blossoming of Celtic midfielder Stuart Armstrong into one of the country’s foremost players was accentuated by his goal in Sunday’s Old Firm derby, and capped off by Strachan naming him in the Scotland squad yesterday.

Armstrong has yet to win a senior cap for his country, but he is odds-on to feature alongside clubmate Scott Brown in the Scotland midfield for the must-win game against Slovenia next Sunday night.

He has certainly pushed his way to the forefront of the national coach’s mind, and Strachan says that a change in his character on the field has played a part in helping him become the player he is today.

“I think he’s a different personality now,” said Strachan. “He’s become a personality on the football field. He has enjoyed being that personality.

“I think what he wanted to do before, and I might be wrong, is be a good team player. But he had more than that in him.

“What he is trying to do now is be the best player on the pitch first and then be a good team player. I think it was the other way about before. This personality has grown.

“The fact he has been with Celtic. It has not gone all that smoothly. It hasn’t been a great time for him. He has had to take a few knocks, get on with it, come back. That has improved his character. His character has been built up and he has been a big personality on the pitch.

“He was just a lovely fellow. Me and my wife went to a dinner and he made an acceptance speech and we all went what a lovely lad he is, but I’m afraid we have to turn into devils on the pitch and my wife said ‘I know that’.

“So, you don’t have to be a devil but there has to be a devil inside you or this personality devil, and I think that personality has grown because he joined Celtic and had to deal with what comes with that.”

The attacking qualities that Armstrong possesses from midfield have also been noted by Strachan, with a goal threat from the middle of the park crucial to the success of his preferred 4-2-3-1 formation.

“He has moved position,” he said. “That is the first thing you have got to get right because the position that he was in previously was wide in a three at times. That has changed.

“He has gone to that central midfield position which I always thought was his best. He has an engine that means he runs into positions and picks the ball up. Some people stand in positions, he runs into positions.

“He runs beyond strikers as well which is good. He has got the taste for goals now which is why he has come to the fore. When you score goals you get recognised.

“Stuart has five shots on Sunday and all five were on target and that’s good going.”

It is unlikely though that either Armstrong or Brown will feature in the friendly match against Canada at Easter Road next Wednesday night.

The Celtic players in the extended 30-man squad will be granted some extra recuperation time after their visit to Dundee on Sunday.

“It will probably be a day and half before they are ready to do something,” Strachan said. “I would rather be ready with the lads on the Monday, ready to go again, prepare that team from the Monday.

“So they will probably not be playing. That is why [the squad] is a bit bigger. There are also one or two grumbling injuries that players have had that we know about. You protect that as well.

“I thought it was better to have everybody in the squad. Rather than have a smaller squad and then calling people in.”