Niall Quinn finally admitted defeat last night in his battle against a back injury.
The Sunderland striker has been ordered to rest and is certain to miss Saturday's match at Chelsea.
He is also out of the Republic of Ireland's internationals against Cyprus and Andorra later this month.
Quinn, who has played through the pain barrier in recent weeks, was given the verdict following a scan.
Now Sunderland's bid to qualify for the Champions' League may hinge on whether the 34-year-old gets the all-clear from specialists at the end of the month.
Quinn said: "I've had a couple of months of it and we've tried injections. It is so hard to walk away and take a complete rest."
Worries over the Irishman will inject new urgency into manager Peter Reid's pursuit of new signings.
Reid has just returned from Argentina, while No.2 Bobby Saxton flew to Paris recently to check on transfer targets in France.
Quinn's absence will inch powerful striker Kevin Kyle closer to the first team squad following his return from a loan spell at Rochdale.
The 19-year-old has also played for Darlington and Huddersfield this season, but has told Reid that he wants to end his days as a loan ranger.
Kyle said: "I've been out on loan a number of times and it has helped my game, but I want to concentrate on my career at Sunderland now.
"Loan moves allow you to learn about the pressures of football and playing in front of crowds, but I think my game improves more when I'm here because I'm learning from Niall Quinn and Danny Dichio all the time.
"I'm not giving up hope of a first team appearance this season. If I keep doing well and working hard, I know I could get a chance.
"The manager has proved he will give young players a chance if they do well and that's good to know."
l Sunderland have established links with top Swedish club BK Hacken, who have sent six of their talented teenage players to train with the club, start of an unofficial agreement between the two clubs.
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