“THAT’S a snapshot of what Mikey can be.” The words of Republic of Ireland manager Stephen Kenny after Celtic winger Mikey Johnston – who is currently on loan at Portuguese side Vitoria Guimaraes – made a hugely encouraging debut from the bench for his adopted country on Wednesday night.

Johnston made an immediate impact in the Emerald Green as he jinked one way then the next before unleashing a low shot that came back off the post to teammate Chiedozie Ogbene, who ultimately tucked home the winner against Latvia in a 3-2 thriller at the Aviva Stadium.

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Johnston thrilled the Dublin crowd again later on too as he thrust his way into the area, fooling two opponents with his fleet of foot and being denied a debut goal at full international level only by a desperate block from a Latvian defender a couple of yards from goal.

READ MORE: Mikey Johnston Celtic future addressed by Ange Postecoglou

His performance had the Irish fans buzzing with anticipation over the talent they may just have poached from their Celtic cousins, but manager Kenny’s tempering of his words – and his choice of them – were telling. A ‘snapshot’ of what he could be. For all too often in his career to date, that has been what Johnston has shown to the world.

His technical ability has never been in doubt, but so far, the 23-year-old has failed to produce the sort of form he showed in an Irish jersey during the week - and at times in the green and white hoops - on anything like a consistent enough basis.

That is why, after all, he is currently trying his luck in the Portuguese Liga rather than challenging for a place in Ange Postecoglou’s team. And why the Irish were able to persuade him to represent the country of his grandfather’s birth, so far out of the picture was he with Steve Clarke’s Scotland.

In fairness to Johnston, he has endured his fair share of misfortune in his short career to date. A host of injuries have plagued his progress, and hampered his attempts at nailing down a first-team spot at Celtic under three different managers now, all of whom have spoken in warm tones about the winger.

Neil Lennon may have once famously told Johnston to ‘f*** off’ when he tried to play through an injury at McDiarmid Park, assuring his manager that he was fine and he could make his final substitution before promptly breaking down injured, but his overall opinion on Johnston was a positive one.

Indeed, when he eventually recovered from what proved to be another long-term layoff, Lennon said: “We’ve missed him. He is a player that can break the lines, and we’ve been missing that type. So, I’m happy he is back."

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Similarly, Brendan Rodgers saw a player in Johnston.

“He has that special ability to go past people, that speed that takes him away, and he’s got confidence and a bit of charisma on the field,” Rodgers said.

“He doesn’t need an injection of confidence, that’s for sure. He’s got a lovely arrogance when he plays.”

Though, he qualified his compliments with constructive criticism about how he had to back up his individual talent with concessions to the collective good.

“There’s no top team in the world that plays with freedom and players just going out and playing,” he said.

“You play with a structure and there’s moments in the game when your qualities come into it. He knows now that you can’t run forward if you can’t run back.

“We will see in time. I can see a great future for him as long as he wants to learn.”

Those remarks were made a little over four years ago now, and it is hard to say whether in all that time Johnston’s game, or his career as a whole, have moved on all that much.

What about the current Celtic manager’s perspective? Here is what Postecoglou had to say about Johnston when considering sending him out on loan last summer.

“I think with him there is definitely a talented footballer there, but sometimes you just need a different environment to help that happen,” Postecoglou said.

“I just think for him and his career, some time away playing in a different environment, enjoying his football and bringing out all the potential we know he has might suit him.”

Since then, as well as making his Republic of Ireland debut, Johnston has made seven starts in 16 league appearances for Vitoria Guimaraes and has bagged three goals and three assists across all competitions.

Perhaps more pertinently, Johnston has managed to remain relatively healthy, featuring in all but five of his loan side’s matches so far this season.

So, while he would like to be starting more games, he is getting on the pitch more regularly than he would have been had he stayed in Glasgow this season. The question is though, can he do enough between now and the summer to convince Postecoglou he should stay with his parent club next term, or should he finally admit defeat in his bid to establish himself with his boyhood heroes?

Many Celtic supporters may have felt his time at the club was already up, but that exciting cameo for Ireland may just have reminded a few of them of what they and many Celtic managers have always known; there is a player in there.

Getting the best out of himself on a regular basis – and not just showing his ability in snapshots - remains his biggest challenge. And the biggest obstacle to his chances of a career at Celtic.