Fletcher faces between four and six weeks on the sidelines after injuring his ankle in the early stages of Scotland's 2-1 defeat to Wales on Friday night. In a best case scenario, the Sunderland striker could be available for the last two or three games of the season.
However, if further tests to Fletcher's right foot reveal a need for surgery, he will be sidelined for the remainder of the campaign. The 25-year-old, who returned to Wearside over the weekend, has not sustained any broken bones, but his ligaments were damaged when he fell awkwardly and was stretchered from the field at Hampden Park.
He is due to undergo a second scan once the swelling has subsided later this week, and that will reveal whether he needs an operation to repair the problem. Either way, Sunderland boss Martin O'Neill will have to tackle the most critical spell of his side's season without his leading goalscorer.
Fletcher has scored 11 goals in 28 Premier League appearances since completing a £12m move from Wolves last summer and has been the spearhead of the Black Cats attack for the majority of the campaign. With Sunderland just four points above the relegation zone after a run of seven games without a victory, he will miss a run of matches against Manchester United, Chelsea, Newcastle, Everton and Aston Villa that is likely to prove pivotal to their hopes of avoiding the drop.
In his absence, O'Neill must hope that Danny Graham puts his poor start to life in a Sunderland shirt behind him and rediscovers his goalscoring touch. Graham is still to score his first goal since making a £5m switch from Swansea in January, but the former Middlesbrough trainee is one of only two fit senior centre-forwards on Sunderland's books. The other is Connor Wickham, who recently returned to the North-East following a loan spell at Championship side Sheffield Wednesday, but who has hardly featured at all under O'Neill.
Stephane Sessegnon is another attacking option, although moving the Benin international in from the flank would almost certainly mean abandoning the recent policy of playing with two men up front. Fraizer Campbell, Louis Saha, Ji Dong-won and James McFadden all left Wearside in January, but Graham was the only centre-forward recruited to replace them. Meanwhile, Sunderland have again been linked with a possible summer move for Spartak Moscow winger Aiden McGeady.
O'Neill will look to strengthen his midfield resources this summer, with Republic of Ireland international James McCarthy another player understood to be under consideration. Sunderland are due to have a scouting delegation at the Aviva Stadium in Dublin tonight to watch Ireland's World Cup qualifier with Austria.