Celtic have been in this Mikey Johnston movie before.

The 23-year-old put in a stellar performance for 67 minutes as the Hoops blasted a magnificent seven past Austrian Third Division outfit SK Wiener Viktoria.

Johnston laid the first on a plate for Johnny Kenny to get the ball rolling and helped himself to the third goal by tucking the ball neatly away while under pressure. He then set up James Forrest for the sixth before the opening half was done with a cute cutback after a fine one-touch passing move as Celtic made light work of their opponents.

It begs the question: could he yet end up a regular starter at Parkhead?

At 23, he seems to have been around the fringes of the Celtic first team forever. Potential is a big word in football; fulfilling it is another altogether.

However, salvation could yet be at hand.

Now there are some Celtic supporters out there who will say Johnston will never cut it as a first-team player. Others will argue that he has not had a consistent run of games to prove his worth and that injuries have blighted his progress.

READ MORE: Detailed Celtic player ratings as Reo Hatate and Yosuke Ideguchi impress in seven-goal pre-season rout

Both points can be true of course but, ironically, Johnston actually still has the time on his side to make a telling contribution and to raise his game to a level that could see him become a fixture in Ange Postecoglou's rip-roaring, free-scoring, never-boring Glasgow Celtic side.

Now about that salvation. It could well come in the form of new first-team coach Harry Kewell.

Former Ross County and Falkirk midfielder Davis Keillor-Dunn played under the Australia legend at Oldham Athletic. As well as being a perfectionist, Keillor-Dunn insisted that Kewell would work wonders with the wingers at Parkhead and take them to the next level.

"Harry will take to Celtic like a duck to water,” Keillor-Dunn told The Celtic Way recently. “I watched them a few times last season and I just feel he is a perfect fit for that club.

“Celtic are relentless going forward and they are continually creating chances. I have watched the boy Jota a few times too. Once he gets to work with a player like that he can take him to the next level.

“That's why it wouldn't surprise me to see a quick turnaround in terms of the wide and attacking players' performances and goals ratio as soon as Harry steps in the door at Celtic."

Celtic Way:

This is where it gets interesting. That last sentence is particularly pertinent if you happen to be named Johnston and want to have a future at Celtic.

Kewell himself was as vociferous as they come during the first of the team’s pre-season friendlies. Both he and Postecoglou were never done shouting. The phrase ‘two-touch’ was heard constantly, while Johnston received all sorts of encouragement and cajoling from Kewell throughout.

If the winger is wise he will seek specific counsel from Kewell. Keillor-Dunn did at Oldham and it improved his game.

“He is one of the best coaches I have worked with,” Keillor-Dunn added. “He really helped my game as I played a similar position to him and I got more one-to-one time than anybody.

“He played at the highest level possible and he knew the position inside out. I can really understand why Harry is going into Celtic as he is the kind of guy who can take the club to the next level in Europe. He knows what that arena is all about. He knows the level and the standard required to compete at the Champions League level."

Johnston is therefore going to be learning at the feet of a coach with a track record of one-to-one work. He also accomplished a whole lot as a player too – the former Leeds United and Liverpool man is a Champions League winner after all.

READ MORE: Inside Harry Kewell's obsessive pursuit of perfection

If Kewell can somehow polish and smooth the rough diamond that is in there, then there may be hope for Johnston after all at Celtic. It will also represent a significant – and swift – win for Kewell as Postecoglou’s newest lieutenant.

One swallow does not a summer make but Johnston was badly in need of a morale-boosting Celtic performance like the display he put in against SC Weiner Viktoria.

Yet the Celtic supporters probably feel like they have experienced enough false dawns when it comes to the 23-year-old. The time for saying that Kewell has made a real impact on him will be when he is turning in the same kind of performances on a consistent basis when the games get tougher and the opposition is ratcheted up a notch.

Postecoglou clearly sees talent in Johnston that may well be worth persevering with too. Remember it was he who picked Anthony Ralston up, shook him up and turned him around before turning him into something new.

Ralston's resurrection last season was meteoric, bordering on miraculous. Can Kewell work the same magic on Johnston? Only time will tell.

If he does then the mercurial winger would surely be the first in the queue to sing the new first-team coach's praises… followed closely by the rest of Paradise.