Valencia suffered a suspected fractured and dislocated left ankle during United’s Champions League clash with Rangers last night.
Ferguson said: “It’s a similar injury to the one that Alan Smith had here (in 2006), so Antonio is out for the rest of the season.
“He has gone to hospital, but it looks like a dislocation and a fracture. It’s a bad one and will keep him out for a long time.
“He seemed to dig his toe in the turf and when we saw the Rangers player waving we knew it was bad. It was an innocuous challenge and we didn’t expect that.”
Smith was out of action for eight months after suffering the ankle injury against Liverpool at Anfield in February 2006.
