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Manchester City could be without Sergio Aguero for their pivotal clash with Liverpool in just under a fortnight with the Argentine's absence for their upcoming games shining an awkward spotlight on the surprising early season difficulties of Pep Guardiola's side.

Guardiola confirmed ahead of City's Champions League tie against Marseille (on CBS All Access) that Aguero would be out for at least two weeks with a hamstring injury, a timescale that would mean the Citizens' all-time top goalscorer would be unavailable for the visit of champions Liverpool to the Etihad Stadium on Nov. 8.

Aguero returned from a near four-month spell on the sidelines with a knee injury in the 1-0 win over Arsenal on Oct. 17 and scored in the 3-1 victory against Porto four days later. However the 32-year-old could complete only half of Saturday's 1-1 draw at West Ham United before being withdrawn.

"It will be two or three weeks, Sergio [Aguero] and [Benjamin] Mendy as well," Guardiola said in his pre-match press conference.

"Sergio was injured in the last game, muscular. When you are out for four or five months with a knee problem you always have a risk when you come back.

"We tried to handle it as much as possible, just 50-55 minutes every game. But it was not possible. It depends on the injury. We expect 10-15 days for sure minimum, or it could be three weeks or a month.

"We were incredibly patient and didn't force the doctors. People told me he was ready but we knew he was not for Arsenal, we knew he was not in the best condition but without strikers that we had, it was important that he played 60 minutes but we tried to rest him when the muscle started to be tired. 

"Unfortunately one action in the first half was unlucky because he wanted to stop a long shot at West Ham and it happened."

Aguero's absence will heighten the goalscoring burden on City's other forwards at a time when Gabriel Jesus is also sidelined with an injury to his quadriceps. It is a burden that so far this season they have surprisingly struggled to bear.

A City side that has averaged 101 goals across the last three seasons has eight to its name after five games this term and has only scored once in each of their last three games, a run in which they have been held to draws by Leeds United and West Ham.

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Guardiola appeared to acknowledge that his team could do with another player to put the ball in the net having fielded 17-year-old forward Liam Delap twice this season.

"Maybe we considered it and thought about it and another type of striker but we could not," the City boss said. The club did what they can.

"You know when you decide to buy a striker they have to be at the level of Aguero and Jesus and we could not afford it. This is the reality. I'm not saying the club didn't want to do it in any position because they wanted to make as strong a team as possible but we thought Sergio was coming back, we didn't expect Gabriel's injury -- sometimes it happens."

It is not just in finishing chances that City struggle, this season they have not found the same creative thrust that has been a hallmark of their football under Guardiola.

Despite leading the Premier League in terms of possession per game -- 62.8 percent, per fbref -- City's expected goals per 90 (xG per 90), a metric that assesses the quality of chances a team creates, is only the 10th best in the competition. 

At 1.38 xG per90 City are far below their average tally for last season -- 2.45 xG -- and their two title-winning campaigns.

City saw winger Leroy Sane and playmaker David Silva depart the club last season, replacing the former with Ferran Torres from Valencia. Phil Foden was long viewed as the natural successor to the latter but so far he has predominantly featured in a wide role.

The 20-year-old and Raheem Sterling are City's joint-top scorers in the Premier League this season with two goals to their name.