Aguero is set to be back for their FA Cup clash with Birmingham City.
Guardiola said, "Only I know how I miss him. Just look at the numbers of the quality he has in the box - he is unique. Unfortunately he had a really tough injury and what is important is his mood is exceptional, better than ever.
"He is an important part of the group, incredibly loved and the feeling is that in the last 10 days and 2 weeks his knee has been good after training and this is the best news we could hope for. He's going to start and if he can play 90 minutes it will be great, 60 will be great, 30 will be great - the important thing is good quality minutes. He will start from the beginning and after we will see.
"It will be great to have Sergio fit in the best possible condition. He is so optimistic, saying he will have a good season and score lots of goals. We don't want to create pressure but most of the games we need him as a striker. The most important thing is the consistency we have shown in the last three games.
"We changed the way we played after the West Brom game and we have to show the consistency we have shown in the last three games. That's why we need players coming back, we cannot sustain this effort for 14/15 games."