The North London club will travel to Greece on December 9 requiring a better result than the 3-2 win which was achieved by Olympiakos at the Emirates Stadium in September if they are to overtake Marco Silva's side in Group F of Europe's premier club competition.
After the 3-0 victory over Dinamo Zagreb on Tuesday night, Bellerin said: "I think the team knew it was a very important day today and we had to turn up.
"Everyone did that.
"Now we have to play for our lives, but this was an important test for us to be alive in the Champions League. The team responded very well."