Foster started the campaign with high hopes of becoming United's No 1 goalkeeper.
Sir Alex Ferguson felt confident enough about his progress to proclaim his belief that the former Stoke man would go to the World Cup as England's No 1 as well.
But the season has turned into a disaster for the 27-year-old.
Wrench: Foster will be gutted when the time comes to walk out of Old Trafford
Given first crack at filling the void created by a pre-season injury to Edwin van der Sar, Foster made two high-profile blunders, first in the Manchester derby, when United were only rescued thanks to Michael Owen's dramatic late winner in the sixth minute of injury time, then the following month against Sunderland when he was at fault for a Kenwyne Jones goal that proved crucial in the title race.
Although Fabio Capello did not lose faith, and picked Foster for successive internationals against Belarus and Brazil, the goalkeeper chose to highlight the discrepancy of a career that saw him installed as first pick for his country yet fall to third choice for his club.
On Monday he was reduced to becoming a penalty shoot-out hero in United's reserve team title triumph over Aston Villa.
And, while Foster accepts any move away from Old Trafford is a step down, he knows it is inevitable.
'You never want to leave Manchester United,' he told the Manchester Evening News.
Out of favour: Foster has slipped down the England pecking order this season
'If you leave this club you are only ever going to go down. But I want to be playing football. I am not interested in just hanging around and I would go if the club wanted to sell me.
'If they are happy to accept a bid then you have to read between the lines and realise you are not really needed and move on. It would not be the end of the world for me.'
Ferguson has said he sees Foster being part of his first-team squad next season.
That looks to be highly unlikely though, with the possibility of a loan move on the agenda, possibly to Birmingham if, as expected, they are not able to get Joe Hart back from Manchester City.
Foster knows he will lose out to Hart in the battle to secure a World Cup spot, with David James and Robert Green also set to make the trip to South Africa.
'I don't think there is any chance of South Africa now,' he said. 'If he were to pick me it would be very unfair on some of the other goalkeepers.
'I have not played a first-team game for a good few months and some of the English lads out there like Joe Hart and Robert Green have been doing fantastic.'
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