Arsenal defender Sead Kolasinac will be sidelined for up to 10 weeks with a knee injury sustained in Wednesday's friendly win over Chelsea.
The left-back was withdrawn 20 minutes from full time in Dublin and is expected to be unavailable until October.
He could miss as many as eight Premier League games and two Europa League fixtures, with the Gunners setting a minimum recovery timeframe of eight weeks.
Kolasinac's setback comes just over a week out from the club's season opener at home to Manchester City on August 12.
Aaron Ramsey is expected to return to training in the week leading up to that match after missing the Chelsea clash with tightness in his right calf.