Manchester City boss Roberto Mancini expects Roque Santa Cruz to be sidelined for a month with his latest calf injury.
The Paraguayan lasted just four minutes of his comeback at Everton on Saturday before going down with the same problem that caused him to miss three games over the Christmas period.
Although Mancini does not believe Santa Cruz will need an operation, the City chief did confirm the £18million summer arrival from Blackburn will be out of action for a month.
If Mancini's assessment proves correct, it will rule Santa Cruz out of both legs of the Carling Cup semi-final with Manchester United, Sunday's FA Cup fourth round tie at Scunthorpe plus the Blues' next three Premier League games.
"It is a big problem for us and him," said Mancini.
With Emmanuel Adebayor currently on indefinite compassionate leave, it could lead to a recall for Benjani, who was only on the bench at Everton despite impressing on his return to first-team duties.
Mancini will also be denied the services of new-boy Patrick Vieira tomorrow.
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.
And, despite the magnitude of tomorrow's contest, Mancini 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. "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."