RONNY DEILA has told Tom Rogic he can become a top class player once he manages to last 90 minutes.

The Celtic manager has been delighted with the progress of the Australian who has emerged from nowhere to become one of his team's key players of this season.

Rogic has managed five goals in 16 games since returning to pre-season fit and free of injury for the first time in a year, after being given a final opportunity by his manager to prove himself.

But Deila believes the 22-year-old playmaker still has a bit to go, not in terms of skill, but with regarding his stamina which has let him down in some matches since his return to the fold.

The Parkhead boss said: "Tom improves all the time. I am really happy with him. He works very hard in training and you can see that being transferred into games.

"But he still needs to last a game, a whole 90 minutes

“There have been too many times when he gets tired. It has been difficult for Tom to feel as good late on in game as he does at the start.

"He has missed a lot of football, which we can't forget. So he needs more games.

"And once this fitness comes, he will be an ever better player and he is at the top level right now."

Deila is sweating over the fitness of Rogic ahead of this Saturday's visit of Kilmarnock in the Ladbrokes Premier League.

The Australian international, a substitute in his country's 3-0 World Cup qualifying win over Kyrgyzstan last Thursday, pulled out of the following match against Bangladesh and returned to Scotland after he picked up a thigh injury.

With Stefan Johansen struggling for form, Celtic could do with having their Aussie available.

Deila said: "Tom has a lot of things he can give to the team.

"He has a good touch, has scored some important goals for us and he has a lot more still to give."

One player who should definitely be available to Deila is Jozo Simunovic who has trained with the Croatian Under-21 squad for the past week.

The centre-half injured his ankle against Molde after just a few minutes and there has been a fear that the 21-year-old's start to his Celtic career would be continually affected by injury.

The £3.5million signing has made just four full appearances since he joined Celtic at the end of the August transfer window.

This has been a frustration for Deila who has been desperate to forge a partnership between Simunovic and Dedryk Boyata in Celtic's central defence.

The Celtic manager said before the international break that Simunovic would join up with the Croatian set-up and expected him to return fit and ready to play for his club.