Arsène Wenger admits that Roma's comeback against Barcelona last night was a 'warning' for him and his team in a pre-match press conference.
Roma beat Barcelona 3-0 and went through on away goals after the tie ended 4-4 on aggregate.
Barcelona let a three-goal cushion slip, and Wenger doesn't want this to happen to his Arsenal side as they look to guard against complacency against CSKA Moscow.
The Russian side were comfortably dispatched by Arsenal as they ran out 3-1 winners in north London, thanks to a Lacazette brace and a stunning Aaron Ramsey chip.