SIGNS of progression will count for nothing if Scotland doesn't qualify for Euro 2016, believes the assistant manager Mark McGhee.

There is a feeling that the national team is gradually getting better under Gordon Strachan, with the two victories over Croatia, as well as strong performances against Belgium, England and Germany, all being forwarded as proof of incremental improvement.

Ahead of Friday night's key qualifier against the Republic of Ireland at Celtic Park, however, McGhee believes any celebration of how far Scotland have come since Strachan succeeded Craig Levein as manager would be premature if the current qualifying campaign does not conclude with the side claiming a berth in the European Championship finals in France in two years' time.

"I don't think we've achieved anything yet," said McGhee. "Any feeling that there is a new mood around the team is still to be consolidated. We can go a long way towards doing that if we get a positive result on Friday night. Equally, that can evaporate quickly. We have a lot of work to do before we can really believe that is true. We have a long way to go.

"Results like beating Croatia are incremental. It's another little step towards the next step and getting a more positive attitude going into each game. It gets the players behind the manager and the fans behind the players. I think we are on the right track but it's not a done deal yet.

"We have made some progress but it has still to manifest itself in a real positive outcome and that would only be in qualifying - whether it's beating Ireland, drawing with Poland, it's irrelevant. The only thing that matters is qualifying. If we do that, we can say we've improved."

McGhee played down talk of Friday night's encounter being a "must-win" for Scotland but admitted the dynamic of Group D had changed with Poland beating Germany and the Irish also taking a point from the world champions. Scotland, with four points from the opening three games, have yet to similarly chalk up a result that would significantly enhance their qualification prospects.

"This is not a pivotal game in terms of us qualifying or not qualifying. Anything could happen in this game, positively or negatively, and we could still qualify or not qualify. There's been a lot of quite positive feedback from performances and recent results. But the fact is, all we've achieved so far is the minimum that would have been expected of us. We've beaten Georgia at home, we got a point from Poland, which I think after us beating Poland over there last year people hoped we would get at least. That's all we've got, after we lost to Germany. At the moment, we've not really done anything more than what people would have expected.

"On the other hand, Ireland in a sense have got a point more than maybe people would have expected, and they've beaten Georgia away from home which is still going to be a big ask for any of us. So, I think we've still got it all to prove. If we can get a positive result we can start to believe we actually are on the up, because I don't think until now we feel confident we've got any right to say that, as all we've done is achieve the minimum so far.

"I expect Germany to come back steamrolling in the second phase of the group. The fact Poland got those three points against them, changes things. We might be looking at having to beat Poland at home, whereas if they hadn't beaten Germany a draw might have done us. It's hard to extrapolate it any way and every way but the best way to look at it is that we are playing Ireland and there are three points up for grabs. They are the only three points we can affect."

Such is the significance of Friday night's game that it is so far completely overshadowing next Tuesday's friendly against England, the first match at home against the Auld Enemy since 1999. McGhee feels that is only right.

"Absolutely no disrespect to the England game, it's not irrelevant, but it's on a different level from the Ireland game. This is the most important game of our tenure, there's no doubt about it. It's a huge opportunity for both teams to take the advantage if one of us could win it. It's all about qualifying for France. We could beat England 6-0, but it doesn't get us to France. This is the game."

Hearts' Callum Paterson became the latest young player to be given a taste of senior international football when he was called up to replace the injured Phil Bardsley. With Rangers' Lewis Macleod also in the squad, and Celtic's Callum McGregor and Ryan Gauld of Sporting having been given similar opportunities earlier in the campaign, McGhee believes it is a worthwhile exercise, whether the new recruits end up featuring in matches or not.

"I think there are a number of players that, as we go along, we would bring in and get to know and have a wee look at. There are some of the young lads that are in the under-21s at the moment, like Ryan Fraser, and others that we are watching and keeping tabs on. It's a good process.

"Stevie May has proven that. He came and trained brilliantly. We all took a step back, we didn't quite expect him to be as good as he was at this stage. But there's no hesitation, if he's good enough we'll have it. The manager has proven that is true by bringing him back again."

Robbie Keane is someone at the other end of his playing career but McGhee, who gave the Irish striker his debut as a 17 year-old with Wolverhampton Wanderers, believes the former Celtic player will still be one to watch on Friday night. "I always believed he could be special. Even at that age he was sensational and he's had a sensational career. One of the things that has impressed me about him is that over the years he has matured. He has really become a man, coming from being a kind of Jack the lad little Irish boy, to quite a serious and respected individual, captaining his country. It's a fantastic rise. He'll be relishing this game, going to Parkhead, for sure."