Injured Smalling ruled out of Euro 2012
"Chris has suffered a bad injury," Ferguson told a news briefing before his side's final match of the season against Sunderland on Sunday.
"It is a torn groin muscle injury and he will miss the European Championships. We are assessing what to do at the moment but it is certainly a bad injury."
Ferguson said Smalling suffered the injury against Swansea City last week but there was more positive news concerning striker Danny Welbeck, who will be available for the tournament even though he is missing Sunday's match with an ankle injury.
"He is still out just now but he should be fit for the Euros," Ferguson added.
Smalling, 22, who has three international caps, was expected to be included in recently appointed England manager Roy Hodgson's 23-man squad when it is announced on Wednesday.
England face France, Sweden and co-hosts Ukraine in Group D of the June 8-July 1 tournament, which is also being hosted by Poland.