MANCHESTER, England - Manchester City defender Nathan Ake is expected to miss up to 11 weeks after undergoing surgery to repair a foot fracture, yet another injury blow in City's underwhelming season.

"When you have surgery it's serious," Guardiola told reporters ahead of Saturday's Premier League clash at Nottingham Forest. "He has struggled a lot this season with the problems in his feet."

The Netherlands international had surgery on Tuesday after he aggravated the injury, which has bothered him for much of his career, during Saturday's FA Cup fifth-round victory over Plymouth Argyle.

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City travel to Forest with both teams looking to earn Champions League qualification next season. Forest are third in the Premier League table on 48 points, one point and one place ahead of Guardiola's men, whose goal of claiming a fifth consecutive league title unravelled weeks ago.

"There are many different clubs fighting for this target. Everyone wants to be in the Champions League next season for many reasons," Guardiola said. "If it doesn't happen for us then it's because we haven't been good enough and the other teams deserve it."

The Spaniard was asked whether the pressure is less since his team is not in realistic contention for the league title.

"Pressure is always there in big clubs," Guardiola said. "You have to pressure yourself to do your best no matter what you're playing for.

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"It's different, but the reality is that we try to finish in the top four. Tomorrow we have an opportunity to climb and help secure this target."

City are also without defenders John Stones and Manuel Akanji, but newcomers Abdukodir Khusanov and Vitor Reis are expected to feature on Saturday.

"The impact of Khusanov was really good," Guardiola said. "Vitor was really good against Plymouth. Now some centre backs from the academy are coming to play with us."

City midfielder Jack Grealish has been the subject of negative headlines about his lifestyle recently, with former Manchester United striker Teddy Sheringham among the critics.

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"There have always been players over the years that worked okay and played hard and their football abilities fell off a cliff. Jack's a little bit in that mould at the moment," Sheringham told Prime Casino.

"They won the treble and he celebrated on that front and it doesn't seem like he's got back into his football mode yet. He needs to … otherwise his career might slip away."

Guardiola had little say when asked about Grealish.

"He's so famous. People follow him," he said. "I have nothing to comment."