Sergio Aguero's mood is "better than ever" as he tentatively nears the end of an injury nightmare, according to Manchester City manager Pep Guardiola.

Guardiola confirmed City's all-time top scorer will start Sunday's FA Cup third-round tie against Birmingham City at the Etihad Stadium as he looks to put the after-effects of meniscus surgery behind him.

Aguero underwent an operation in June and has been forced to manage ongoing discomfort in the joint since a hamstring injury at West Ham curtailed his initial return in October.

Despite being ravaged by a coronavirus outbreak among their squad, City head into the weekend buoyed by their two finest performances of the season - a swashbuckling 3-1 win over Chelsea preceding a 2-0 win against rivals Manchester United in the semi-finals of the EFL Cup.

Four minutes from the bench at Stamford Bridge was the sum of Aguero's action across the those games, as he was an unused substitute at Old Trafford.

Nevertheless, his goalscoring prowess has been an obvious miss across the course of the campaign. In their most recent title-winning season, City averaged 2.6 goals per game in the Premier League with Aguero in the side.

That has fallen to 1.6 in all matches this time around, with a win percentage of 53.9 per cent, set against 84.8 with Aguero in harness two seasons ago. Shots per 90 minutes are also down from 18.1 to 15.6 when the two data sets are compared.

"Just look at the numbers, the quality he has in the box, Sergio is unique," Guardiola told a pre-match news conference.

"He has a tough, tough injury. The important thing is his mood is exceptional, I would say better than ever.

"It's important that the feeling, the last two weeks, his knee's reaction was really good after training. This is the best news we can have.

"He’s going to start, the minutes his performance level or knee will dictate. What's important is good quality minutes, as much as possible, we start from the beginning and after we'll see what happens.

"It will be great to have Sergio fit. He’s so optimistic. He says 'I will score goals' and that is the most important thing."

Aguero is out of contract at the end of the season, as is fellow fans' favourite Fernandinho.

The 35-year-old Brazil international has returned to his customary central midfield position this season, having deputised at centre-back for much of last, and completed the scoring with a sweetly struck volley against United in midweek.

Following the departure of David Silva over the close season, Fernandinho has stepped up as club captain and impressed Guardiola greatly with his leadership skills.

"With the players in this part of the season, everything is open," Guardiola said, when discussing the prospect of the veteran earning a fresh deal.

"I am more than impressed with the first captain role of Fernandinho, he is leading in an exceptional way. In the good moments and the bad, bad moments.

"If everyone can take an example of what he has done so far, the team will be stronger."

Pressed for examples of how the quietly spoken star commands the dressing room, Guardiola replied: "How he talks with his mates, how he talks with my assistant coach, before the game, at half-time.

"Not just talking to players about football matters, in life, how to behave in training, every single day. He's the first who proves that he's able to do it.

"That's why he goes to Old Trafford, plays holding midfielder there. It was not easy for Bruno Fernandes to control him.

"At the beginning of the season he stepped forward and showed how to be a captain."

City will have Ederson, Ferran Torres and Tommy Doyle available for selection once more, provided they returned negative COVID-19 tests on Friday.

The trio tested positive ahead of the postponed Premier League match at Everton on December 28.