SUNDERLAND face a major battle to land either Paul Heckingbottom or Michael O’Neill, despite having identified the pair as their preferred managerial candidates.

Martin Bain’s search for a permanent successor to Simon Grayson is now in its third week, and having drawn up an extensive shortlist, the Black Cats chief executive has settled on Heckingbottom and O’Neill as his top two options. However, as things stand, he has not received formal permission to speak to either.

Sunderland’s interest in O’Neill is complicated by the amount of competition for the Northern Ireland manager’s services. His current employers at Windsor Park want to keep him despite Northern Ireland’s failure to qualify for next year’s World Cup in Russia, but the Scottish FA made a formal approach to the authorities in Belfast yesterday to request permission to speak to O’Neill about their own managerial vacancy.

Scotland dismissed Gordon Strachan after he failed to even make the World Cup play-offs last month, and the SFA regard O’Neill as the ideal person to replace the former Middlesbrough manager. O'Neill took Northern Ireland into this month’s play-offs, where they suffered a controversial 1-0 aggregate defeat to Switzerland, and guided his side to last summer’s European Championships in France, where they made it to the knockout stages as they ended a 30-year wait for an appearance at a major tournament.

To further complicate things from a Sunderland perspective, O’Neill is also the subject of strong interest from both the United States and Rangers.

Bain would like to hold face-to-face talks with the 48-year-old to assess his interest in a possible position at the Stadium of Light, but in order for that to happen, he would first have to reach an agreement with the Northern Irish FA.

O’Neill has previously spoken of his desire to return to club management, with his only previous experience in that sphere having come with Brechin City and Shamrock Rovers. However, he lives in Edinburgh, and the rest of his coaching staff are also based in Scotland. As a result, the opportunity to take over the Scottish national side could appeal, especially as the SFA are willing to significantly increase his current earnings, which are understood to be around £500,000-a-year.

As well as pursuing O’Neill, Sunderland are also attempting to line up a formal interview with Heckingbottom, although that is also proving problematic.

The Barnsley hierarchy have outlined a determination to do all they can to hold on to their current manager, even though he is only on a 12-month rolling contract worth around £100,000-a-year, and sources close to Heckingbottom claim the former Darlington and Hartlepool United defender has privately expressed concerns about the financial situation at the Stadium of Light.

Heckingbottom turned down the chance to move to Nottingham Forest in March because he was worried about the off-field situation at the City Ground, and while he accepts he will have to leave Oakwell at some stage in order to progress his career, he is adamant he will not walk out of a secure position in South Yorkshire unless he is convinced his next job offers a realistic chance of success.

Sunderland would be willing to increase Heckingbottom’s wages in an attempt to lure him to Wearside, but neither Bain nor Ellis Short are likely to be able to provide any guarantees about funding in January with the latter having publicly admitted he is willing to hold discussions about a possible sale of the club.

Ally McCoist is the third leading contender on Sunderland’s shortlist, and Bain has already spoken to the former Rangers boss to discuss his thoughts.

The fact McCoist has not received a job offer following his interview suggests the Sunderland hierarchy are keen to initially look elsewhere, but the Scotsman is known to have impressed at the interview stage and his candidature is not at an end. Significantly, McCoist has spelled out his strong desire to take over on Wearside, and that remains the case despite this week’s events.

With little chance of an appointment in the next 24 hours, Robbie Stockdale will remain in caretaker charge for Saturday’s home game with Millwall. The former defender worked alongside Billy McKinlay as Sunderland suffered a 1-0 defeat at Middlesbrough prior to the international break, but with his former partner having left to join the coaching staff at West Ham United, he will be in sole caretaker charge in two days’ time.

Sunderland have not recorded a home victory since mid-December, and Millwall boss Neil Harris admits his players will be looking to take advantage of their opponents’ sorry state when they travel to Wearside this weekend.

“It’s really tough to change a mindset,” said Harris. “We found that here. We finished a season flying at home, winning massive games against Wigan and Charlton and drawing against Derby who were in the play-offs at the time, and you think you’ve cracked it. Then we start the following season and lose the first four in a row at home. It’s really tough.

“We can use (Sunderland’s poor home form) to our advantage. The law of averages says it will change for them at some stage – we’ve just got to make sure it’s not Saturday.”