Sunderland will almost certainly have to win their fight against relegation without Steven Fletcher. The £12m Scotland centre-forward will find out later this week whether he requires surgery to repair the ligament damage injury he sustained to his right ankle while on international duty on Friday night.

Even if an operation is not needed, Fletcher is expected to be either ruled out for the remainder of the season or sidelined for around six weeks. Swelling around the injury has made a definitive diagnosis difficult but, after undergoing further scans, Sunderland's key striker is likely to see a consultant on Tuesday or Wednesday who will provide an accurate prognosis.

With his side only four points above the relegation zone and not having won any of their past seven games, Fletcher's absence is the last thing Martin O'Neill needs.

Sunderland's manager, who also expects that knee trouble will sideline Lee Cattemole the rest of the campaign, faces a run of testing games against Manchester United, Chelsea, Newcastle, Everton and Aston Villa over the coming weeks.

Although his goals have dried up since the New Year, Fletcher has scored 11 times in 28 Premier League appearances for O'Neill's team since arriving from Wolves last summer and is by far Sunderland's most dangerous forward.

In his absence the team will have to rely on Danny Graham, a £5m signing from Swansea in January, and the £8m England Under-21 international Connor Wickham, neither of whom have scored a league goal for Sunderland this season. Meanwhile Stéphane Sessègnon, who can also operate in attack, has recently been hampered by groin trouble.