Giroud was watching from home as a goal from £32million summer signing Alexis Sanchez clinched a nervy 1-0 win over Besiktas.
While Arsenal were left celebrating at the Emirates, Giroud has suffered a broken tibia and will not play again for four months.
But the Frenchman's wife Jen tried to keep the striker in good spirits, posting a picture of him recovering during the match.
Gunners fans will be calling for Arsene Wenger to sign a replacement, but the Arsenal boss has suggested he will stick with his current options.
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"You'll ask who we'll buy to replace Giroud. At the moment, nobody," Wenger said.
"Giroud had surgery today for a broken tibia and he will be out for three to four months on the competitive side.
"He'll be out for two months, but the time he needs to comes back is three to four months.
"He'll be capable to play again in the Premier League at the end of December."
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