The 26-year-old was forced off in the 24th minute during the loss at the Etihad Stadium after pulling up in a race with Kyle Walker.
Mikel Arteta admitted after the match that Mari’s injury ‘did not look very good’.
And according to The Athletic, Mari will now miss the rest of Arsenal’s Premier League campaign and could require surgery on his injured ankle.
The report also claims that Rob Holding, who has made just nine appearances for the Gunners this season, is in contention to feature for their match against Brighton on Saturday.
Mari joined Arsenal on loan from Brazilian side Flamengo in the January transfer window but the Gunners have the option to make the deal permanent for £10 million this summer.
Arsenal are also without David Luiz for the next to games after the Brazilian’s red card against City.
The former Chelsea defender has also not agreed a new contract with Arsenal, and he could still leave the club when his current deal expires at the end of the month.
Meanwhile, Granit Xhaka also suffered an injury during the opening stages of the loss to City but The Athletic reports that the Swiss midfielder could return before the end of the season.
The defeat against Manchester City has left Arsenal eight points behind fourth-placed Chelsea.
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