The midfielder signed a one-year contract extension earlier this month that will take him past his 40th birthday.
That will see the most decorated player in English football join Gordon Strachan and former United team-mate Teddy Sheringham in an exclusive veterans' club.
And Ferguson believes that, given the Welshman's current fitness level, Giggs could well continue to rewrite the record books.
"Ryan is an exceptional human being," Ferguson told US radio station Sirius XM.
"He has never carried any weight, has never suffered a serious injury and never misses a training session. He is still at the head of the pack during pre-season.
"He just has this insatiable appetite to continue playing. He will play next year and who knows he could possibly play for another year after that.
"I am sure he will get to 41 and still be playing because he is such a fit lad."