Arsenal now have it in their own hands to qualify for the knockout stage of the 2015/16 UEFA Champions League.
Arsene Wenger's Gunners produced a comfortable 3-0 victory over Dinamo Zagreb at the Emirates Stadium to move within three points of Olympiakos who they meet in their final Group F fixture.
Nacho Monreal had intercepted a poor defensive pass from Leonardo Sigali prior to cutting back for Sanchez to finish clinically from just outside the six-yard box.
With just over 20 minutes on the clock, the North Londoners went three ahead courtesy of Sanchez's second which came in the form of a close range finish after he had controlled Joel Campbell's delightful through ball before rounding Zagreb keeper Eduardo.
The victory was only Arsenal's second in five European outings this term but keeps alive their hopes of joining group leaders Bayern Munich in the Round of 16 provided they can defeat Olympiakos in Athens on December 9.
The Greek side were hammered 4-0 in Munich meaning Arsenal simply have to overcome them on their home soil in order to make it 16 knockout phase qualifications in a row for Wenger's men.
2015/16 UEFA CHAMPIONS LEAGUE - GROUP F SCORES