GORDON STRACHAN today assured Leigh Griffiths his Twitter reaction to not being called up for Scotland's friendly in Norway in November is not the reason he has been omitted from the squad to face Poland next month.

The striker was upset when, having been left out of the initial squad for the friendlies against the USA and Norway, Kris Boyd was brought in after Jordan Rhodes, Steven Fletcher and Ross McCormack pulled out ahead of the win in Oslo.

Griffiths tweeted: "Gutted with three call-offs and I ain't got called up to the squad."

But Strachan insists this had no bearing on the player failing to make it into the 24 for the match in Warsaw on March 5, even though the official squad list shows only Fletcher, McCormack and Steven Naismith as strikers.

Strachan said of Griffiths' tweet: "I didn't even know about that, until you told me.

"It is understandable. It was nothing more than you would get in a conversation with your friends at a dinner party.

"But, because of things like Twitter, you don't have a dinner party now, you have a kind of Twitter party.

"And that's all right. So long as no one is being derogatory, or being negative towards the squad, myself or the other coaches, then that's fine."

Griffiths' has won four caps, having been given his first when Billy Stark was in interim charge for the match against Luxembourg in November 2012.

His most recent appearance for his country came in the defeat to Belgium in September last year.

But Strachan believes the 23-year-old's transfer to Celtic from Wolves on the final day of the January window will help lift his game to a different level.

And, given time to settle into his new surroundings - Griffiths has made just one sub appearance and one start for the Hoops - Strachan reckons he will force his way right back into contention.

As he prepared to fly out to Nice for this weekend's 2016 European Championships qualifying draw, the national team boss said: "Leigh doesn't need to do anything different to get back into the squad.

"All any player has to do in their career is get better all the time, and he has a great chance at Celtic to get better.

"Leigh has done absolutely nothing wrong to not be in this squad.

"It's just that I have picked a certain amount of players for the system we want to play at this moment. And that's it, really."

Strachan was concerned Griffiths had slipped out of the first team at Wolves prior to his move back to Scotland.

But, he understands circumstances rather than form were the reason.

Nevertheless, Strachan makes no attempt to hide his pleasure that another player eligible for his quad could soon be playing in the Champions League.

HE SAID: "It's great to see him playing at this level, rather than the level he was at. I am not speaking about the Wolves level, but the division he was in."

Not that his club, whether it be Hibs on loan or Wolves, was ever an impediment to the professionalism and commitment Griffiths showed whenever he was invited to join up with the national squad.

Strachan said: "I like Leigh as a person, and he could not work any harder than he does when he comes to training with us."

That's the minimum Strachan asks of everyone invited to work with the national squad.

The inclusion for the first time of 19-year-old Andrew Robertson is a timely reminder to anyone harbouring aspirations to be called up or recalled that, if you are good enough, you are old enough.

The Dundee United left-back has only played top-flight football for seven months, since bouncing back from being released by Celtic as kid and kick-starting his career in the unpaid ranks of Queen's Park in the lowest tier of the Scottish Senior game.

Of course, Robertson's position is notoriously difficult to fill, as there has been a general dearth of left-backs.

Certainly the wealth of talent available in midfield makes that a much tougher department to break into, as Robertson's team-mates at Tannadice, Stuart Armstrong and Ryan Gauld, have just been reminded after missing out for this match.

But Strachan refutes that simply being a left-back has been the reason for Robertson's accelerated promotion to his squad.

"I don't think we are short in that area," said Strachan, who spent years trying to adequately fill that position while in charge of Celtic.

"Lee Wallace - who has not made it this time - has done all right, Steven Whittaker has done well for us, and Charlie Mulgrew has played there for us, and he is playing in the Champions League.

"So, I don't think we are short of options or that it has been a weak position for us."

It is this competition for places which Strachan wants to see in every area of the side.

And, while having to call half a dozen players prior to the squad announcement to explain, 'You're playing well, but I just don't have a space for you this time around' is never a pleasant job, it is an indicator the man who took over from Craig Levein 13 months ago is finding strength in depth.

The door remains open, and the invitation is there for any player to step through.

Strachan said: "There is no identikit to getting in the squad.

"You can be 33. You can be 16. The point is, can you make us better? Do you suit the style we are going to try and play?

"That's it really. So, when I was asked: 'Did you select Andrew Robertson because he was a new face?' I replied, 'No, I never even thought about that'."

The return of one well-known face, Darren Fletcher, gives Strachan particular pleasure.

And the man who has showed remarkable bravery to overcome ulcerative colitis while at Manchester United will provide the kind of leadership and example which Strachan wants the newer recruits to his squad, like Robertson, to follow.