Arsenal have been dealt a blow ahead of Saturday's crunch meeting with Leicester City after midfielder Dani Ceballos was ruled out with a hamstring injury.
The Spain international limped off during the second half of Wednesday's draw with Vitoria in the Europa League.
And the Gunners have now confirmed that, while the full extent of his injury is not yet known, the Real Madrid loanee will not be part of the squad for the trip to the King Power Stadium.
Ceballos has become a fan favourite at the Emirates Stadium since his arrival on a season-long deal from Santiago Bernabeu over the summer despite his 17 appearances for the club only yielding one goal and two assists thus far.
Reports suggest Madrid are keen to keep hold of him when his loan deal expires given some of his more impressive performances, though his relationship with manager Zinedine Zidane has not always been the best.
The 23-year-old's absence means Unai Emery will need to shuffle his pack ahead of a match that the Arsenal boss can barely afford to lose.
Pressure has built on Emery over recent weeks, with the Gunners having won just two of their last nine Premier League matches while also exiting the Carabao Cup at the hands of a youthful Liverpool team.
Wednesday's performance in Guimaraes did little to lift the gloom around the north London outfit, with Bruno Duarte netting a deserved stoppage-time equaliser for Vitoria after Shkodran Mustafi had opened the scoring 10 minutes from the end.
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As such, defeat against Brendan Rodgers' side may spell the end for Emery, with such a result meaning Leicester would be nine points clear of the Gunners in the race for the top four after just 12 games of the season.
Ceballos missing the trip may, however, allow for Mesut Ozil to again earn a start after the 2014 World Cup winner was reintroduced into the first-team picture over the past few weeks.
Ozil found himself out in the cold for much of the opening weeks of the campaign, with Emery not even naming him among the substitutes for a series of matches.
But a strong showing in the Carabao Cup game against Liverpool was followed by just his second Premier League start of the season against Wolves in last Saturday's 1-1 draw at the Emirates.
Ex-Real Madrid playmaker Ozil was then rested for the midweek trip to Portugal, meaning he may be in contention for another start come the weekend.