Manchester City boss Pep Guardiola will continue to ease Sergio Aguero back into first-team contention despite missing his star striker in a dour Manchester derby draw with United at the weekend.
The Argentine returned to Guardiola's team midweek off the bench against Marseille after a prolonged spell out due to injury.
But the manager was unable to call on Aguero's services against United after he suffered a bout on gastroenteritis.
City struggled in front of goal in his absence, mustering just two shots on target as Saturday's clash at Old Trafford ended in a 0-0 stalemate.
But Pep used the example of Nathan Ake to show why Aguero would not be rushed back before he is 100 per cent ready.
"With Sergio it is one step at a time," he explained to reporters. "He made one training session, he was four months out and there are players who, for them, not to be in the squad would not be fair to them.
"That is why sometimes I have to handle the balance of the team. For me it is so tough, to drop Nathan Ake after he was exceptional against Marseille.
"He could not be selected today because there is this rule that there cannot be 19 or 20 players when all the players are available for the squad, some are at home.
"Hopefully Sergio will be back, make more training sessions and as many minutes as possible to come back as soon as possible."
Another player looking to win his way back into Pep's first-team plans is Aymeric Laporte, but he may have to wait his turn after John Stones and Ruben Dias consolidated themselves in the middle of defence during the centre-back's injury absence.
"He deserves to be in the team but John Stones and Ruben also deserve to be in the team," Guardiola said of Laporte.
"They played incredibly well in the last games and didn't make one single mistake.
"Aymeric played so well against Marseille and that is the point - team selection. Nathan Ake played extraordinarily well against Marseille but I have to make a selection. They didn't make mistakes.
"What they have to do is work harder, better and the moment will come, and when the moment comes have a good performance.
"Every player in every squad has incredible skills, like United, Spurs and Liverpool. But it is about how you perform right now. Right now. John and Ruben performed brilliantly, so they play."
City are back in action on Tuesday, when they host West Bromwich Albion at the Etihad Stadium.
Pep's charges currently sit in ninth place in the Premier League, six points behind joint leaders Tottenham and Liverpool having played one game fewer.
