Hargreaves is due to return to Old Trafford on Sept 23 after spending recent months undergoing rehabilitation at the clinic of renowned knee surgeon Richard Steadman in Vail, Colorado.
Ferguson admits that he is hopeful of seeing Hargreaves back in action, for the first time since his outing at Chelsea on Sept 21 last year, from early November.
Ferguson said: "With the Champions League squad, we wondered what we should do about Owen Hargreaves and whether we should put him or Zoran Tosic in the 25-man squad.
"It was a dilemma, but we came down on the side of Hargreaves because, having taken the medical advice, we think he will be available for the last three Champions League games.
"That will be the time when we want to push him back into action. He is such a versatile player, a man who can play in so many positions, that he could be a very important player for us at that time of the season. That's the reason he is in."