Manchester City manager Pep Guardiola said he still felt responsible for his team's Champions League struggles as it starts a fresh bid to win the elusive European trophy in the group stage at home to Porto on Wednesday.

City was knocked out last season by Olympique Lyonnais in the quarterfinals, making it the fourth successive time the Etihad club had failed to progress beyond the last-eight.

“I felt so responsible for this,” Guardiola told a news conference on Tuesday. “How the club and players fought, I was not able to drive them.

“The reality is every team and manager has to dream with high expectations but the reality is we have not performed to the level. I feel so bad for the players but this is a new chance and we will start again.”

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City has had a troubled start to the Premier League campaign with a 5-2 thrashing by visiting Leicester City and a 1-1 draw at Leeds United but Guardiola's side regained momentum at the weekend with a 1-0 win at home to Arsenal.

The Spaniard is expecting another stern test against the Portuguese champion.

“Porto are one of the strongest teams in Portugal, their mentality is to win every single weekend,” said Guardiola.

“We need to be more consistent and improve on the little details. The reality is to win the home games is so important for qualification.”

Kevin De Bruyne, Gabriel Jesus, Aymeric Laporte and Benjamin Mendy are sidelined for City through injury but full back Oleksandr Zinchenko has recovered from a muscle problem.

“We expect Kevin and Aymeric to return in the next few weeks,” Guardiola said. “Gabriel, maybe a little bit longer and we hope they will come back soon and the team will grow.”