Manchester City needs to invest during the January transfer window due to injury problems and a faltering Premier League campaign, manager Pep Guardiola said on Monday, acknowledging it may have been a mistake to rule out signings in the summer.

City's title defense looks all but over after six league defeats has left it sixth in the standings and 12 points behind leader Liverpool who has a game in hand.

Guardiola's side has missed Ballon d'Or-winning midfielder Rodri, who ruptured knee ligaments in September, and has suffered injuries to defenders John Stones and Ruben Dias.

"In the summer the club thought about (signings) and I said: 'No, I don't want to make any signings," Guardiola said ahead of Tuesday's league game at Brentford.

"I relied a lot on these guys and thought I can do it again. But after the injuries maybe we should have done it."

City has not made a significant signing in January since the arrival of Aymeric Laporte for 57 million pounds ($69.67 million) from Athletic Bilbao in 2018.

Guardiola could not confirm whether a deal has been done to bring in Lens defender Abdukodir Khusanov.

"The club didn't announce anything. I don't know," he said.

"Rodri is impossible but the other ones (injured players) I want back. If it would have happened I wouldn't be going to the transfer window this season. Absolutely not.

"We would not be in the position that we are but we struggle all season. It's not just Rodri, we have a lot of problems in the back four. That is the reason why the club is thinking we might do this transfer."

After City's 8-0 FA Cup win over Salford City on Saturday, Guardiola revealed that Walker had asked to leave the club, but the manager had no update on the situation and the right back could be in the squad at Brentford.

"No news. I'm not going to add anything, no more news. I only have Brentford on my mind," Guardiola said.

"We will decide this afternoon after training."

The cup win was a third consecutive victory for City, a welcome return to form after Guardiola's side had previously won only once in 13 matches in all competitions.

"We won three games. Before it was impossible to win one," he said.

"Now we won three, and that helps us. But the reality is we won against a team in the last game for the difference of the Premier League and League Two (fourth-tier), the badges of both teams, and many reasons we should win.

"We have to wait to see if we are who we are. The mood is better. Tomorrow we have an enormously difficult game."

Reuters