CELTIC are understood to have sounded out Roy Keane over their soon-to-be vacant managerial position as they seek to make a swift appointment ahead of this summer’s Champions League qualifying matches.

Sources in Ireland stated last night that the Republic of Ireland assistant manager, who turned down the opportunity to take over the reins at the Ladbrokes Premiership champions two years ago, has been contacted over the possibility of replacing the outgoing Ronny Deila.

However, much of what happens at Celtic over the next few weeks may be tied to what happens at Everton.

Roberto Martinez seems certain to leave Goodison Park after a troubled campaign and Martin O’Neill, the former Celtic manager, has become the favourite to take over.

For months, O’Neill has repeatedly insisted that he is not concerned about the fact his contract with the Football Association of Ireland is entering its closing months and it seems almost inevitable that there will be a parting of the ways after this summer’s European Championships in France.

Any concrete move that Celtic may make for Keane could be complicated by O’Neill moving to Everton. It could clear the way for the former midfielder to take charge of the Republic of Ireland and he would be seen as a popular successor.

The other alternative is that Keane could go with O’Neill to Everton and continue the relationship they have enjoyed at international level.

Keane has spoken recently of his keenness to get back into club management, with the assumption being that he would opt to be a number one rather than an assistant.

David Moyes, also on Celtic’s shortlist, is believed to be in contention for the Everton role with Michael O’Neill, taking Northern Ireland to Euro 2016, still on Celtic’s radar.

There are a number of names in the frame for the Celtic job with bookmaking firm Ladbrokes reporting a substantial degree of interest in the former Liverpool manager Brendan Rodgers, whose price tumbled from 20/1 to 7/2 over the course of yesterday.

Rodgers made it last week that he is seeking a return to management and described Celtic as “one of the great iconic clubs in the world”.

"This is the biggest gamble we've had on the next manager to replace Deila and it's looking like fans are expecting to hear the Rodgers roar next season,” said Ladbrokes spokesman David Macdonald.

Deila, meanwhile, has spoken of the need for a siege mentality to exist within the champions’ dressing-room next season and insisted a united front will make it difficult to take the Ladbrokes Premiership trophy from the Parkhead club.

Deila is facing up to the closing weeks of his time in charge and has expressed the view that external forces are forever attempting to drag the club down.

“Everyone around us wants to tear us apart and make us individuals, but, together, we are so strong,” he said. “If this club is united, it is going to be so hard to take that trophy away from us.”

Deila insists there was also a special reason why he invited the entire backroom staff to take part in the on-field celebrations which followed the 3-1 win over Hearts at Tynecastle at the weekend.

“It showed that Celtic is not just one player or the fans. It’s everybody,” said Deila in an interview with the Celtic View.

“That is why I brought all the staff out, so that people can understand how many people are behind this.

“We’ve got five-in-a-row and it’s very important. The most important thing is to be champions of Scotland, which opens doors for the club, but it starts with that foundation and that is what we have done.

“I feel proud in a lot of things we have done here. The boys have stood behind me all the time with every decision and any time I wanted to try something new.”

Meanwhile, Celtic have confirmed that they will introduce a safe-standing area at Parkhead from the beginning of next season.

The club have sent out season ticket renewal forms to supporters containing information on plans to install rail seats over the course of the summer in the corner of the Lisbon Lions Stand, which currently houses the Green Brigade supporters’ group.

Celtic were granted permission to introduce a standing area last June and announced at that point in time that they intended to accommodate 2600 people in that section of the ground.

Celtic have also announced a freeze on season ticket prices for next term.