Olivier Giroud has been ruled out of Arsenal's Champions League play-off against Besiktas on Tuesday with a foot injury, manager Arsene Wenger confirmed.
Arsenal are awaiting the results of a second scan on Giroud's ankle, amidst fears the France striker coud be sidelined for three months.
A fuller assessment of how long Giroud will be out should come after he has seen a specialist on Tuesday.
"Olivier will not play against Besiktas and will see a specialist, then we'll make an announcement of how long he'll be out," Arsenal manager Arsene Wenger said.
Giroud, 27, suffered the injury in the Gunners' 2-2 draw at Everton on Saturday, shortly after ensuring a share of the points by scoring Arsenal's 90th-minute equaliser at Goodison Park.
He needed an extra scan to reveal the full extent of the damage once swelling in the injury, which hampered initial investigations, had gone down.
Wenger may now be forced to dip into the transfer market in search of a replacement if the Frenchman faces an extended spell on the sidelines.
"It can be (a long term injury). We'll see tomorrow. I don't know (if it's broken). It's sad for us," Wenger said.
Summer signing Alexis Sanchez could operate as the loan striker against Besiktas, while Yaya Sanogo, Lukas Podolski or Joel Campbell could also start.