The Red Devils boss explained that a plate put into the Ecuadorian's ankle following a serious injury last season will remain in place for the time being
The 26-year-old had a plate inserted into his ankle early last season following a serious injury, and it had been reported that it will soon need to be removed.
However, Ferguson has refuted this, telling ESPN: "I don't where the story about the plate coming out of his ankle has come about - it's never been on our agenda, it's never been discussed."
"We know he has a plate in his ankle, but at the moment it stays there.”
The manager went on to praise the Ecuador international, who hit a crucial 80th-minute strike against Blackburn to help the Red Devils go five points clear at the top of the Premier League.
"As far as his form is concerned, what can I say? He's been unbelievable since he's come back. He's been brilliant,” he continued.
"When he first came back into the fold after long term injury I put him at right-back occasionally with Nani in the forward position.
"Once he got a few games behind him his form has been tremendous. When you get players who are hitting form at this time of year, their best form as well, it's a bonus."
United have the opportunity to extend their lead at the summit should City fail to win at third-placed Arsenal on Saturday.
But the Scot refused to look beyond this weekend’s match against QPR, who have beaten both Liverpool and Arsenal in recent weeks.
"I'm not going to get into [predictions about the league title]. I think we have to concentrate on the game ahead and the game ahead is QPR on Sunday at Old Trafford - we just need to focus on that," he commented.
"We have to respect QPR because their last two results have been fantastic, beating Liverpool after being 2-0 down and beating Arsenal 2-1. They are very good results for them.
"Knowing Mark Hughes, he's a fighter and his team will fight for survival. As much as I am looking forward to the game it's going to be a hard one. We expect a hard one, that's the best way of looking at it."