Thomas Vermaelen has undergone surgery on his left ankle and is expected to be out for at least a month, Arsenal confirmed this afternoon.
Vermaelen underwent the surgery yesterday in Stockholm after suffering the injury in the Gunners' 2-1 win over Udinese on August 24.
The Belgium defender, who missed eight months of last season with an Achilles injury on his right foot, will miss the north London derby at Tottenham on October 2 and the club's first two Champions League group stage matches.
While losing Vermaelen for such crucial games is a blow for the Gunners, manager Arsene Wenger will be pleased that his star defender is not out for longer.
Some reports this morning had suggested Vermaelen would be out for two months, but the club played down that speculation this afternoon.
An Arsenal statement read: "Thomas Vermaelen is expected to be back in training with the first-team squad in around a month.
"Vermaelen has undergone a minor procedure to remove an inflamed plantaris tendon from his left ankle.
"This is the same treatment that he had on his right ankle in January this year and has nothing to do with his Achilles tendon.
"The action was taken after consultation with specialists who advised this was the best thing to do to prevent it becoming a persistent problem."
Vermaelen missed the Gunners' 8-2 mauling at Manchester United nine days ago but has otherwise been an ever-present at the heart of Wenger's defence this term.
Per Mertesacker, who signed just before the transfer window shut last week, is now likely to have to step up to fill Vermaelen's place in the team over the next two months.
The German, who arrived at Arsenal from Werder Bremen for £8million, also has competition from Laurent Koscielny, Johan Djourou and Sebastien Squillaci at centre-back.
The north London club have conceded 11 goals so far this season and currently sit fourth from bottom of the Barclays Premier League table with one point.
Mertesacker was one of several late arrivals at the Emirates Stadium this summer as Wenger looked to compensate for the departure of Cesc Fabregas and Samir Nasri by adding to his squad.
Mikel Arteta, Yossi Benayoun, Andre Santos and Park Chu-young all joined the club just before the transfer window shut and Carl Jenkinson, Gervinho and Alex Oxlade-Chamberlain arrived earlier in the close season.
Arteta had spent six years at Everton before moving to the Emirates Stadium in a deal thought to be worth £10million.
The 29-year-old Spaniard, who started off his career at Barcelona, is confident he will be able to do slot in to the club's style of football.
"I have always been a big admirer of the Arsenal philosophy, the way they play, the way they do the job, and it's always exciting watching Arsenal play. In England there is no better team to watch than Arsenal," Arteta told Arsenal's website.
"Hopefully I will not take long to adapt but obviously you need to meet new characters, new personalities and new players with different abilities so you need to pick that up as soon as possible to get an understanding on the pitch.
"But I have been watching a few videos and have got some work done before training and hopefully that will help me."Reuse content