Ferguson: Valencia could return in February
The Ecuadorian broke and dislocated his ankle in Tuesday's 0-0 Champions League draw with Rangers, with television channels unwilling to show replays of his fall and the sickening direction his foot was pointing in.
He had surgery on Wednesday, which Ferguson said had been successful.
"The break was clean and we were delighted to announce that. It was a major concern for us at the time," the club's website quoted the manager as saying.
"There's ligament damage but we're looking at the end of February, which is better than we thought on Tuesday night. He's a strong boy and he's very positive about it - being positive helps in these situations."
Ferguson added that United, who face Liverpool in the Premier League on Sunday, were well equipped to manage without Valencia.
"It's a blow but in the context of the squad we have we should cope with it. We have players like Nani, (Ryan) Giggs, Park (Ji-sung), (Gabriel) Obertan, Bebe... there are options there."