Vieira set for Man City debut in ten days
The Italian is not willing to risk him against United, or at Glanford Park, with next week's second leg now the earliest Vieira is likely to be seen in a City shirt.
"It is better for us, and for him, that he can go and be ready in a week or 10 days," he said.
The French midfielder has been unavailable since arriving from Inter Milan after picking up a calf injury in his final game for the Serie A outfit.
"It is better that we do not take risks in this situation. I would like it that when Patrick does come back he can play until the end of the season."