The Spanish forward suffered an ankle injury during United's Emirates FA Cup defeat against Watford at St. James' Park, joining a growing list of injury absentees on the sidelines.
Benítez will remain without a trio of midfielders in Jonjo Shelvey, Ki Sung-yueng and Mohamed Diamé, as well as having Paul Dummett and Karl Darlow unavailable for their meeting with the Citizens.
"The midfielders are still very close, but not ready for this game so it's more or less the same," Benítez said. "Darlow is getting better and I think he will be fine by the end of the week.
"The only one we have lost is Joselu, with a twisted ankle after a bad tackle (against Watford). It is not serious but he is not available for the game. No Shelvey, no Ki, no Diamé."
After exiting the FA Cup at the fourth round stage, United must now switch their full attention to facing the reigning league champions, with Pep Guardiola's in-form squad scoring 28 times in their last six games in all competitions without conceding a goal in the process.
And, although Benítez is aware of the talent their opponents bestow, the Magpies boss remains hopeful of gaining a positive result against his Spanish compatriot.
Benítez added: "We were disappointed (to go out of the cup) but we have to concentrate on a very, very difficult game. When you play against Manchester City, you have to forget and make sure you do the right things on the pitch.
"If you analyse the way they can play, they have three or four of the fastest players in the Premier League. They won the title because they're a very good team and manager. They have everything but we realise that and we'll try to use our strengths.
"It is not just about defence. For myself, balance also means to attack but, depending on the players that you have, you can manage in one way or another. If you play really high and have a go against the fastest players in the league, they can kill you within two counter-attacks.
"If you wait deep all the time they can pass the ball around and they can kill you so you have to find that balance and we will try to attack, counter-attack, tackle and take advantage of the set pieces.
"I'm confident that we can do well (on Tuesday) but at the same time, we have to do everything perfect to have a chance."
