Roy Keane ended a short, stimulating era at Sunderland yesterday with his resignation two years, three months and 100 games into the job but there was no time for reflection among those who would succeed the 37-year-old Irishman as manager.

The Sunderland chairman, Niall Quinn, has already received numerous enquiries and the bookmakers have installed Sam Allardyce as the early favourite to be Keane's successor.

One of Allardyce's favoured coaching phrases is POMO – Position Of Maximum Opportunity – and his immediate availability and willingness to do the job means he is an obvious contender. Supporters of Allardyce will ask Sunderland to focus on the job he performed at Bolton Wanders, rather than his stint at Newcastle United which ended in January.

There is no suggestion from Sunderland that Allardyce merits a favourite's position, but it is an indication of the limited domestic choices that Allardyce is there alongside Alan Curbishley, who is understood to be interested but has a compensation issue with West Ham. Hull's Phil Brown is another mentioned but Steve McClaren, already mooted by some, is most unlikely to be Sunderland's next manager.

There is no expectation that an appointment will be made in the next 48 hours. In the meantime, the coaches Ricky Sbragia and Neil Bailey, aided by Dwight Yorke, will lead Sunderland at Manchester United tomorrow evening. Sbragia worked with Allardyce at Bolton.

The successor will inherit a team in the relegation zone – unless Sunderland win at Old Trafford for the first time since 1968 – but a squad assembled under Keane that is underperforming and which holds potential for better.

That was part of Quinn's message yesterday. There was no tone of recrimination from Sunderland, though Keane’s resignation was followed by a flurry of speculation that he had registered his final decision by text message.

Rather than speak directly, Keane is alleged to have texted Quinn that he had decided to leave. Sunderland were insistent that the communication had been through the proper channels and that a fax confirming Keane’s decision had been received yesterday morning from Keane’s solicitors.

Communication has not been straightforward between Keane, Quinn, Sunderland’s players and the club’s owners, the Drumaville consortium, over the course of Keane’s time at the Stadium of Light, so this speculation was to be expected.

As Quinn reiterated yesterday in praising Keane for his work at the club, Keane is “box office” and has always attracted widespread fascination. This sort of probing will not be unexpected by either party. Keane is reported to have had his contract paid up.

Sunderland may have foreseen Keane’s departure over the past few days but the reality still affected Quinn. He has bent over backwards to accommodate Keane, not just this week, but over the course of Keane’s tenure and Quinn said at the club’s training ground, in the seat where Keane would normally be: “You hear terms like amicable in situations like this – this is actually the way it is.

“Roy Keane hasn’t been sacked because we’ve a bad team; he’s resigning because we’ve a good team he feels he can’t bring any further. There’s a big difference there.”

Quinn explained some of the activity that followed Keane’s remarks last Saturday night after the 4-1 home defeat by Bolton. Keane voiced self-doubt loudly following Sunderland’s sixth defeat in seven games. “He officially resigned this morning,” Quinn said. “We’d been in negotiations for the last few days to see if we could provide a solution together and at all times every conversation was qualified by what was in the best interests of the club. Ultimately, Roy’s decided in the best interests of the club that somebody else takes the next chapter of where this club goes. Everybody at the club has got huge respect for Roy. He lifted this place off its knees. He’s had a tremendous influence and it’s a shame that today things happen this way. I spoke many times about Roy and I being in a partnership and it feels like a partnership has dissolved. I wish him real well in the future.”

Quinn referred back to where Sunderland where when Keane appeared at the stadium on 28 August 2006 – bottom of the Championship. Quinn was in the dugout that day as Sunderland beat West Bromwich Albion. Keane had agreed to come then and though he won his first two games and, swelled Wearside’s diminished pride, Sunderland were only 12th at the turn of 2007. But they then won 16, drew three and lost one of the next 20 games to finish top.

Promotion was Keane’s and so was Premier League survival the next May. This season was about kicking on and five weeks ago Sunderland were ninth in the table. But form, and their manager’s faith in himself and the team, has unravelled rapidly since, which led to yesterday’s decision.

Who’s next at Sunderland?

Sam Allardyce: 6-4

Big Sam's reputation took a dive at Newcastle and he would relish the chance to rekindle the halcyon days he enjoyed at Bolton. Spent year at Sunderland in 1980s.

Alan Curbishley: 11-2

Favourite on fans' message boards. Out of work since quitting at West Ham in September, over George McCartney's sale to the Black Cats.

Phil Brown: 8-1

Local lad who has engineered Hull's impressive debut season in the top flight after learning trade under Allardyce at Bolton.

Gordon Strachan: 8-1

Dynamic Scot could yearn for return south after easing to three successive titles at Celtic. Match of the Day audiences would welcome return of his post-match outbursts.

David O'Leary: 14-1

Out of work since leaving Aston Villa in 2006 after undoing the good work he did with his "babies" at Leeds. Linked with job two years ago and played with Mackems chairman Niall Quinn for Ireland.

Michael Laudrup: 20-1

Spartak Moscow boss has also been linked with Chelsea, Blackburn and West Ham in recent seasons. Like Keane, a legendary midfielder in his playing days.

and finally... K Keegan: 100-1

Yet to be offered third chance at St James'. Inspired one sleeping North-east giant ... could he do it again?