RONNY Deila said last night that high-level efforts were already under way to persuade Manchester City loan duo John Guidetti and Jason Denayer to stay at the club long term.

While the verdicts over the Norwegian's batch of summer signings have been mixed, the Swedish centre-forward and the Belgian central defender, both of whom have been borrowed from the Eastlands club for a year, have been star turns.

Denayer, the 19-year-old who recently earned his maiden call-up for the Belgian national team, said this week that he watched Manchester City play in the Champions League on Tuesday night and "wants to be back there next season".

Striker Guidetti is likely to be swamped by offers as he will shortly come out of contract.

At the same time he is scheduled to participate for Sweden in the European Under-21 championships.

But Deila, who met with chief executive Peter Lawwell this week, is well aware how much of an asset they could both be for the club.

"We talk and think about it all the time," said Deila.

"These players are doing well so we of course want to keep them. It is simple. We will see what we can get out of them."

Celtic host Kilmarnock today, hoping to follow up a Europa League performance with a league win for the first time this season.

So far Deila has opted for Guidetti, who is ineligible for European football until January, in domestic matches, and used Stefan Scepovic in the Europa League.

But the Norwegian hinted last night that he could be prepared to alter his 4-2-3-1 formation for 4-4-2 and see if the pair can play together.

"I think they can play together," said Deila. "You just have to get the right team around them. It will be interesting - it is definitely something we have to try out one day.

"We will see if Sunday is the right time. They are intelligent players who work well so they could suit each other.

"It is about principles for me, not systems. We have to play the system that suits the players."