(REUTERS) - Arsenal have been handed an injury blow ahead of a packed festive schedule, with captain Pierre-Emerick Aubameyang facing up to two weeks on the sidelines due to a calf strain.

Gabon striker Aubameyang missed their 2-1 defeat by Everton in the Premier League on Saturday (Dec 19) and is set to be ruled out of Tuesday's League Cup tie against Manchester City, as well as Premier League games against Chelsea on Boxing Day and Brighton & Hove Albion three days later.

"We want him back as quickly as possible but he has a small strain," Arteta said.

"We need a few days, I don't know if it's a week or two weeks. It will depend on how the injury evolves."

Saturday's result meant Arsenal have lost five of their last seven league games and lie in 15th place with 14 points, four points clear of the relegation zone.

It is their worst start to a season since 1974-75, raising the pressure on Arteta, who took charge of the club in December last year.

"There is no question, the results are not good enough and not acceptable for the standards of this club and this is the challenge and the fight that we are against," Arteta said.

"It's a really complicated situation, but I am very encouraged from what I see from the players to continue doing what we are trying to do."

Former England captain Alan Shearer said the Spaniard should be worried about his future.

"I wouldn't be sure (if they will stay up). Not with that starting team and the attitude of some of those players," Shearer told the BBC.

"Arteta should be a worried man relying on that group of players."