Celtic hope to persuade Roy Keane to see out his contract by using the 34-year-old midfielder more sparingly but will reassess his long-standing hip problem in the summer.

The Scottish Premier League leaders last night remained privately upbeat about the chances of Keane remaining at Parkhead beyond the summer, but his Glasgow future remains in severe doubt because of the recent worsening of his injury.

While in Dublin on Tuesday, Keane raised the possibility of ending his playing career 12 months before the expiry of the contract he signed with Celtic in December.

Though his hip has proved troublesome for years - and required surgery in 2002 - club sources have revealed the injury appears to have worsened in the past few weeks.

Such timing coincides with the former Manchester United captain becoming a regular in Gordon Strachan's team, and Keane having to adapt to the rigours of playing on heavy Scottish pitches.

With the league title all but sealed, Strachan may opt to use the man who will turn 35 in August sparingly after Keane admitted to feeling sore after Sunday's win at Hibernian.

Celtic say they will reassess the future of the 66-times capped player in the summer.

Keane played his final game for the Old Trafford side last September but has been picked for his new team's last five matches, which included a man-of-the-match performance in a 1-0 Old Firm win at Ibrox.

If there is no further reaction from the injury, Celtic hope to persuade Keane to play a part in next season's Champions League campaign, although he has also described the situation with his wife and children, who are based in Cheshire, as "not ideal".

It was thought when he joined Celtic, Keane would have no trouble playing one game a week in the Premier league. However, Keane said this week that he has been told to "look at the bigger picture" by his surgeon.

If he does end his successful and eventful career in the summer, Keane is set to make his final appearance at his testimonial match between Manchester United and Celtic on May 9th.

The SPL season finishes two days earlier.

However team-mate Stilian Petrov claims the performance of every Celtic player would drop 10 per cent if the inspirational Irishman decides to retire.

Petrov is hoping Keane continues playing because of his influence on those around him.

"He adds something to everybody's game," said the Bulgarian international captain.

"He gets 10 per cent more from everybody. On the pitch he fights and he shows what kind of player he is in training and in the games. He always wants to do his best. He always pushes you and he gives us more concentration."

Defender Stephen McManus agrees Keane would be "sorely missed" should he stop playing. The young Scot said: "Roy is a top player and for as long as Roy decides to play on that's great news.

"It's a great pleasure to play alongside somebody who has played at the top like him.

"He will be sorely missed whenever he goes. When you lose top-class players it's always a shame.

"He demands so much off everybody, which is great, and that improves your game.

"When someone like Roy Keane is having a wee word in your ear, then you've got to listen. He is well respected in the game and he is a top player."

Keane does not look like a man in pain to Petrov, who actually believes he is getting sharper with every week.

"He doesn't look like he's got a problem at the moment," added the 26-year-old.

"He's been having problems and has told us a few times. But every game he looks sharper and we know how important he is for our team with his experience and his name.

"Every time he is on the team sheet other teams wince. I hope he will continue to play on for a few more years.

"You never know what he might do in the future. He is an experienced player and he knows what he wants."

Petrov knows his team-mate misses his family in Manchester but has revealed there is never a complaint from Keane.

He concluded: "It's very hard because he is flying forward and backward all the time.

"He misses his family and we all know that. But he is coping at the moment and he is not complaining."