Sir Alex Ferguson admitted he was shocked when he heard that Rio Ferdinand had got an international recall, and has hinted the defender's fitness may yet prevent him from returning to the England fold.
Ferguson has urged the England staff to follow Manchester United's lead and manage the 34-year-old's workload in both games and training sessions.
The centre-back, who has not played for his country since June 2011, was included in Roy Hodgson's squad to face San Marino and Montenegro.
Ferdinand's international career seemed to be over when, despite injuries to other defenders, he was omitted from the squad for Euro 2012 – with Hodgson arguing it was "for footballing reasons" – and then the England manager said after last month's win over Brazil that he had "moved on".
But the veteran has earned praise for his recent performances for United and is now set to add to his 81 England caps after Hodgson picked him ahead of Joleon Lescott.
"I was as surprised as anyone when I heard that [Ferdinand was in the squad]," said Ferguson.
After several injury-hit years, the defender has started 24 games this season which his manager believes is down to the way United look after Ferdinand and Ferguson hopes Hodgson will adhere to their advice about keeping him fit.
"I need to speak to our doctor," the United manager added. "We prepare Rio in certain ways and he has certain treatments he has to go through.
"The procedures have been the same all season, which has given him fantastic performance levels when he's playing for us. We have to consider that and Rio is considering that. And we'll see what the outcome of that is."
"[Rio] has to make sure he's going to be okay in terms of the number of games he plays. We've been doing that for two years with him. And it's worked. The way we've detailed his training programmes and given him the treatments he needs for the various complaints he has in terms of his back and groin and things like that. So far it's worked very well. We have to look at all these things before Rio decides."