The Chilean supplied two assists for Theo Walcott's two first-half goals as the Gunners opened their winning account in the Champions League this season.
The result made it four wins on the trot for the North Londoners, which inspired the following post from Sanchez on social media.
Feliz por la victoria y por mis compañeros happy for the win and for my team mates . https://t.co/2I7vosIhFV
— Alexis Sánchez (@Alexis_Sanchez) September 28, 2016