Manchester City have suffered a fresh injury blow with manager Pep Guardiola confirming Portugal central defender Ruben Dias has been ruled out for "three or four weeks" with a muscle injury.

Dias, who suffered the injury in Saturday's 2-1 defeat by Manchester United, will miss the entire festive programme and potentially the FA Cup third-round tie with Salford on 11 January.

The 27-year-old also faces a battle to be fit for City's crucial Champions League trip to Paris St-Germain on 22 January.

Dias has already missed seven games with a calf injury this season, adding to a defensive injury list that has seen John Stones, Nathan Ake, Manuel Akanji and Kyle Walker all ruled out at various points, while Ballon d'Or winner Rodri will miss the remainder of the domestic season after suffering a cruciate knee ligament injury.

"It's a muscular problem and he will be out for three to four weeks," said Guardiola.

"After 75 minutes against United he felt something. But he's so strong and wanted to stay on the pitch. Now he's injured."

Guardiola confirmed Stones, Akanji and midfielder Mateo Kovacic have all trained this week and could feature at Aston Villa on Saturday (12:30 GMT), but said goalkeeper Ederson was "a doubt" with an unspecified problem.

"Ederson has been struggling with some niggles in his leg, he doesn't feel completely fine," said Guardiola. "Ederson is so important for us."

Amid City's current run of one win in 11 games, surprise has been expressed about Guardiola's use of youngsters James McAtee and Nico O'Reilly.

City made a point of keeping both players despite numerous loan options. Yet McAtee has made just two substitute appearances - coming on in the last minute on both occasions - while O'Reilly is yet to make his league debut.

But it seems they will stay at the club for the second half of the season, with Guardiola replying "I don't think so" when asked if players might leave during the January transfer window.

The Spaniard said he is "not a big fan" of buying players in January but it is "possible" City will look to sign someone because "the circumstances of this season have been special".

Guardiola's mood was so downbeat in the immediate aftermath of the United defeat it was easy to imagine he might conclude he was no longer capable of doing the job.

He gave his players a couple of days off afterwards and was brighter when he spoke to journalists in his scheduled briefing before the Villa trip.

"We'd just finished a game that we lost in the circumstances and I was not happy," he said.

"I try to be honest about the feelings of my teams. We fell down six times [number of Premier League games without a win], we have to stand up seven. There is no alternative.

"I'm fine. I'm a normal person with feelings like all of us. When the situation is going well we are better but it's normal. I would not go to the press conference if we were 1-0 up and expressing something that I didn't feel."

Former Villa forward Jack Grealish has not scored for City in over a year but Guardiola pointed out he is not the only attacking player struggling this season.

He added: "We are struggling to create a little bit up front, but always I am optimistic about my players that they are going to turn and perform well."