Manchester United confirmed yesterday that Ibrahimovic has signed a new one-year contract at Old Trafford.
The legendary Swede was superb for United last season before a knee injury cut his campaign short in April.
Ibrahimovic is making a speedy recovery and there have been reports that the 35-year-old make his first-team comeback in the coming weeks.
But Red Devils boss Mourinho is being more realistic and is putting on time frame on the striker’s return.
The Special One said: "He will not be ready for the group stage of the Champions League. I don't think there is any chance of that.
"Do we have space in the Champions League list to have him? Yes we have. But I am not thinking Zlatan will play any part in the group phase.
"Hopefully he can play in the knockout phase but for that we need to finish top two.
"I don't want to think about it. I don't even ask. I don't speak with him about it, I don't speak with the medical team about it.
"I just think he will be an extra man for us in the second part of the season.
"I have no idea and I think the right way is to not even think about it, to just let him do his work step-by-step and come back when he is ready."
Mourinho added: "I am really happy he is with us. It shows two things for me. Shows me the dimension of the player and the dimension of the club.
"The dimension of the player because it would be very easy for him to say goodbye, to say it's enough, he had success at Manchester United, then a big injury and good bye.
"He doesn't do that, he wants to follow his other dreams and play football at the highest level.
"A club like Manchester United, in my opinion, has to show how big it is in details and this is a big detail. A player who gets injured in a Manchester United shirt, fighting for Manchester United, the club has to be there for him and I am really happy with club and player."
United, who beat Swansea 4-0 last weekend, host Leicester tomorrow evening.
