I N some ways it was a good time to lose a manager, in other respects the timing was a pest.

Celtic were not caught out by Neil Lennon's decision to walk out on them. They had known for 10 days that a decision their manager had been mulling around for almost 12 months had crystallised in his head. The succession planning, the discussions between Dermot Desmond, Peter Lawwell and the other kingmakers began long, long before everyone else caught up with developments four days ago.

Clubs usually lose successful managers suddenly. They are head-hunted by richer rivals and can be gone within hours, without warning (shedding a poor manager is different, a club has an element of control over the timing of his dismissal). Lennon emulated Martin O'Neill and Gordon Strachan in terms of delivering league titles and some European highlights in a generally successful reign. And he copied them, too, by leaving in a close season.

Celtic have been lucky in that regard, if it ever can be lucky to lose a manager you wish to keep. Not for another 30 days will there be the craic and clatter of the first-team squad around Lennoxtown. Celtic cannot drag their heels on making an appointment because time is precious in terms of getting in ahead of other clubs on transfer targets, but losing Lennon in May does give them some leeway in a window which is open until September.

Still, there are senior figures within Parkhead who do not regard this as a good time to be looking for a manager. That is not a slight on the available (or speculated upon) candidates - chief among them Owen Coyle, Malky Mackay, Roy Keane, Henrik Larsson and Davie Moyes - rather an acceptance that Celtic are not the only sweetie in the tin right now. West Bromwich Albion and Tottenham Hotspur are in the market for a manager. Vacancies might emerge before long at Aston Villa, Newcastle United, West Ham United or Southampton. Mackay and Moyes, in particular, want to see how things settle in the Barclays Premier League in the coming weeks.

It isn't difficult to imagine Desmond having the major hots for Keane right now. When it comes to ticking the boxes on Desmond's managerial checklist, Keane comes closer than the rest. Irish, former Celtic man, experienced, box office appeal off the charts, charisma to burn: Keane has it all. He would be affordable, too, which cannot be said of the more proven Moyes. Would Keane want it? He's already said he has two jobs, thank you very much, and doesn't need to give up his roles as Republic of Ireland assistant manager and media pundit to satisfy any craving to sit in an office at Lennoxtown.

What he would say privately to a persistent Desmond is another matter, though. Keane didn't stay long at Celtic in 2006 but he was impressed by the facilities, the training and the club's performance analysis work. Poor sales resulted in Celtic extending the deadline for season-ticket renewals last week. Appointing Keane would have the queue snaking all the way down the new Celtic Park walkway and along London Road.

Two names are worth recalling when it comes to Desmond and managers: Tony Mowbray and Roberto Martinez. Remembering Mowbray's reign is enough to bring Celtic fans out in a cold sweat. Their record of appointing managers is impressive under Desmond, three good ones out of four ain't bad in anyone's language. But Mowbray's failure to handle Celtic cost him his job and also demonstrated Desmond and Lawwell's fallibility.

Some men grow in charge of an Old Firm club and others shrink. No-one knows how Coyle or Mackay, two managers who have had excellent periods in their careers, would handle the unyielding scrutiny and intrusion which comes with being in charge in Glasgow.

Martinez's name is relevant because he contradicts a misconception about Celtic. The last foreign manager appointed at Parkhead was Jo Venglos 16 years ago but in 2009 the club asked Swansea City for permission to approach Martinez. Identifying a 35-year-old Spaniard with no connection to the club demonstrated that the club is not a slave to the concept of picking "Celtic-minded" managers. Strachan could not be described as such either, of course, but the interest in Martinez was more revealing as it demonstrated that some within the club have been prepared to think outside the box.

This time the appointment has been described as "crucial" because Celtic "must" get into the Champions League group stage. In fact this is a decision which will be made under less pressure than any Celtic board has faced when replacing a manager. Celtic have been downsizing their transfer spend and their wage bill for a decade. Failing to reach the group stage in the infancy of the new manager's reign would accelerate the process, but it would hardly be a job for the emergency services.

Missing out for a year - which they surely will at some stage - would cause no threat to the club nor the inevitability of them winning another league in a year.

What they want is a popular, proven, successful, affordable manager. That's a wishlist they will find impossible to satisfy, whatever the timing.