Arsene Wenger is targeting a strong start from his troops when Arsenal take on AC Milan in the San Siro on Wednesday night.
The Gunners go into the last-16 first leg in good spirits, having seen off in-form Sunderland 2-1 at the weekend to rise up to fourth in the Premier League table.
Wenger believes his side will need to be at the top of their game against the experienced Italian champions, who have lifted the trophy seven times.
Wenger said: "It is a game which, for me, is a real 50/50 where it is very important for us that we have a positive attitude in the first game.
"I believe they will start strong and it is important at the start of the game how much we win our fights in every area of the field.
"It will be very important not to let them on top of us but the way we need to start strong will be very important to us."