Giggs's current deal expires at the end of the season and he turns 40 on 23 November, Wednesday's FA Cup replay against West Ham was his 17th appearance already this term.
And after watching Giggs turn in an impressive display in a 1-0 win, Ferguson told MUTV: "He will play for another year.
"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."
Giggs - told about his manager's comments - said: "I don't feel like that now. I'm enjoying it more than ever at the moment, though.
"The FA Cup at Old Trafford... if you don't enjoy that you need to pack it in."
United's goal came in the ninth minute from Wayne Rooney, who was back in action after sitting out their last five matches due to a knee injury.
The England striker turned in Javier Hernandez's square ball from close range, and after taking the congratulations of his team-mates, then paid his respects to his late sister-in-law, kissing his hands, looking to the skies and raising his arms as he walked back towards the halfway line.
Rooney had the chance to double the lead from the spot but put his penalty high over the bar.
It leaves United with a record of four penalties scored and five missed for the season so far and Ferguson said: "I don't think it is just one of those things. I think we have to improve at that.
"If you get a penalty kick, really... there has been talk about (the good penalty record of) Rickie Lambert at Southampton. That is what taking penalty kicks is about.
"There have been several great examples over the years - (former Southampton midfielder) Matthew Le Tissier scoring 47 out of 48.
"A penalty kick is your opportunity to take advantage of a foul or a handball or whatever and score a goal."