Valencia was stretchered off on Tuesday during United's 0-0 Champions League draw with Rangers after suffering a horrific injury following an innocuous tackle from Kirk Broadfoot.
Initially, Ferguson said Valencia would miss most of the campaign. However, it now appears the damage is not quite as bad as the United boss feared.
"You can never be 100% accurate in these situations and it is a bad injury, but we are looking at the end of February, which is better than we thought on Tuesday,'' said the United boss.
Valencia had an operation on Wednesday evening to put his left ankle back into place after it was fractured and dislocated. Ferguson revealed the Ecuador star had also suffered some ligament damage.
"The operation has been successful and the break was clean, which was the major concern for us at the time,'' he said. "He is a strong boy, who is very positive about it. Being positive helps you in these situations, so we are very hopeful we will get him back then.''
Ferguson, who has no other injury concerns ahead of Sunday's game against Liverpool at Old Trafford, accepts the loss of Valencia is a significant blow. But, in Nani, Ryan Giggs and Park Ji-sung, he feels United have the options to cope.
"Antonio had a great season last year,'' he said. "He was a great signing for us. He is a young player who has been improving all the time. "It is a blow losing good players but in the context of the kind of squad we have, we should be able to cope with it. You always fear when you have a good player out of your team it is going to be a loss.
"But having players like Nani, Ryan Giggs and Park Ji-sung, plus Gabriel Obertan and Bebe means we have options.''
What will benefit Valencia as he begins the long fight for fitness is a positive mindset. That was never better exemplified than by Alan Smith, who suffered similar misfortune during an FA Cup tie at Liverpool in 2006, but whose mental toughness astounded even Ferguson.
"There is a mental part to it,'' he said. "Take the example of Alan Smith. When Alan got his bad injury in that cup tie against Liverpool, he was so positive. He sat in that treatment room at Anfield so nonchalant and relaxed about it. Yet you look at his ankle and think 'God almighty'. That attitude definitely helped him.''