The France international is set to be sidelined until October with an ankle problem.
Arsenal’s website confirmed on Friday that the striker has been playing with the problem over the past few weeks.
The club statement went on to state that Lacazette needs to “rest and strengthen his ankle to regain full fitness”.
Lacazette’s injury will come as a blow to Arsenal after the French striker scored his second goal of the Premier League season in a 2-2 draw with Tottenham Hotspur in the north London derby last time out.
The France star has forged a productive strike partnership with Pierre-Emerick Aubameyang over the past 12 months or so.
However, Lacazette’s injury setback could provide Nicolas Pepe with the chance to cement a regular starting spot in the team.
Lacazette took to Twitter to send a message to Arsenal supporters following his setback.
Lacazette wrote on Twitter: “Already started my rehab and looking to the future.. Thanks everyone for your messages !! #Coyg #Laca 9️⃣♣️”
Arsenal signed Pepe in a club-record £72m deal from Ligue 1 side Lille in the summer transfer window.
The Gunners are aiming to break back into the top four this season after finishing fifth last term.
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