THERE was no lack of conviction in the actions of James Forrest when, having already scored the goal that had wrapped up the first trophy of the season, he pushed away Stefan Johansen and a quite livid John Guidetti to put himself in charge of penalty-taking duties towards the end of the League Cup final.

He missed, of course, seeing a dreadful effort easily saved by Dundee United's goalkeeper, Radoslaw Cierzniak.

For all those signs of renewed confidence he exuded in seizing the ball after being felled in the box by Paul Dixon, the truth is that Forrest remains a fragile figure. Fragile both of body and spirit.

It is a natural by-product of several years spent bogged down by injury and illness. "Irreplaceable" was the word once used by his former manager, Neil Lennon, to describe him. "Unavailable" has generally more accurate.

Ronny Deila, his new head coach, has other, more alarming, terms to detail what the 23-year-old winger's frame of mind has been in recent times as he attempts to overcome his clear physical weaknesses, once and for all, with the help of the Celtic medical team.

"He has been very afraid," said Deila. "When you have been out two of the last four years with a lot of pulled muscles, you get frightened.

"He has been much worse than he is now."

It is easy to understand that degree of fear that now exists in Forrest's make-up, a fear that sprinting full-out will result in another strain or tear, a concern that his body will break down again under duress.

These are issues that have to be addressed by those working hard on helping this undoubted talent fulfil his potential, but Deila stresses there remain distinct physical deficiencies that must be solved if Forrest is ever to live up to his billing.

"It is psychological, but it's also that his body hasn't been balanced," said Deila.

"That's about core strength. It's about how to control high speed, changes of direction.

"He needs to play more football. His physique is not even close to what it should be.

"If he plays 90 minutes, it takes five days to recover because he hasn't played for such a long time. If I push him again, he gets another pulled muscle because he's tired.

"You have to measure him all the time. He has to be honest with his body. We have to build him step-by-step."

Deila can understand why Forrest has been labelled a potential £10m talent in the past. With all this talk of rebuilding him, he sounds more like the Six Million Dollar Man, but the Norwegian remains optimistic about his future.

"I hope, in half-a-year, we can sit and be really, really excited about James Forrest," he said.

"It's been a long time since James has been consistently good and that is because of injuries, but, touch wood, that's six months without a pulled muscle.

"I have been unbelievably patient with him because we have had to build him up from the bottom.

"We have had to build his self-belief back up, create the belief that he won't get these injuries again and we have to take it slowly.

"He is not even close to what he can be as a footballer."

Forrest has still managed to earn a somewhat surprising call-up for Scotland's upcoming matches with Northern Ireland and Gibraltar.

Whether the national coach, Gordon Strachan, believes he is still "a good team-mate", one of his favourite phrases, after that on-field spat with Guidetti in the League Cup final is unclear.

Certainly, Kris Commons, who scored the opening goal in Celtic's 2-0 win, feels it took some of the shine off the day.

"It probably put a little dampener on the way that we won," said Commons, who had been substituted by that stage with the other designated penalty-taker, Leigh Griffiths.

"We are meant to have this good unit, but, clearly, at the end of the game, it looked as though people were doing things on an individual basis.

"I don't think any player - and I don't care how big you are - should throw a strop on a football field.

"I don't think it has ever happened before at Celtic. It's the sort of thing you see on The Footballing Years on Sky. It was like a Di Canio-Lampard moment.

"We've had a little chat about it. I think Craig Gordon is in with a shout (of taking penalties) now."

Is there really a new, established pecking order when it comes to stepping up to the spot, though?

"Yeah," said Commons. "We're going to do some bingo."

The incident certainly reflected badly on Guidetti. With his early scoring form having faded, you get the feeling he is not quite the kind of character Deila wants within his collective. Talk of a permanent contract has been shelved.

"I don't have any problems with him as a character," stated Deila. "He is a funny boy. He is a striker who loves scoring goals and wants to take penalties.

"These things can happen in intense games. That's why it is important to have clear roles.

"I don't think there are too many big egos here."

Egos or not, there is an uncommon willingness around Celtic to talk openly about winning a treble. Deila has been leading the way.

"I think that just shows the confidence the manager has in the group that's playing," said Commons ahead of tonight's William Hill Scottish Cup quarter-final replay with United.

"He strongly believes we're the best team in Scotland. I think we've proved that in years gone by, that we're the driving force of Scottish football.

"We should be reaching finals and giving ourselves the best opportunity to win all three. In previous years, we've probably let ourselves down in the biggest games.

"In my eyes, a double is a successful season, but I feel like the treble is within touching distance and that we can get the three.

"I think we are a better team than last year. We've not reached the top.

"If we do win the treble, we will be looking to do it again next year and the year after then add Champions League group stages and try to get to the last 16.

"You've got to keep striving for greatness."