The 39-year-old, who made his debut for the Red Devils in 1991, earned plaudits for his display in Wednesday's 1-0 win over West Ham United in the FA Cup.
Despite concerns that it could be his final season at Old Trafford, the Welshman is expected to extend his stay by another 12 months.
"He will play for another year," Ferguson told MUTV after the match.
"There are no discerning signs of tiredness or weakness in his game, his quality is still there and he has fantastic balance.
"He has the appetite for it and he is just an incredible human being."
United's reward for beating West Ham is a fourth-round tie at home against Fulham.