Foster revealed earlier this week that he may call time on his United career this summer.
Viewed by many, including Ferguson, as Fabio Capello's likely first-choice for this summer's World Cup in South Africa and felt good enough to be handed an England starting berth in successive matches against Belarus and Brazil, Foster's star has faded dramatically.
He has featured in just one Premier League game in seven months and has accepted his chances of earning a call-up to the 30-man provisional squad Capello will unveil on Tuesday are non-existent.
There seems little doubt he will seek a new challenge this summer, especially now 39-year-old first-choice Edwin van der Sar has decided to extent his own illustrious career by another season.
"I have had a chat with Ben," said Ferguson.
"I understand his dilemma but there is nothing I can do.
"He is a terrific goalkeeper and we will see what the future brings for the boy.
"He has the talent to be England's goalkeeper and we're conscious of that.
"We'd like to help but unfortunately he's not played enough football to get him on that plane to South Africa."