The Gunners must win by two goals at the Karaiskakis Stadium in Piraeus in order to move beyond the group stage of Europe's elite competition and despite it being a tricky task having lost there on each of their three previous visits, Campbell is confident.
The Costa Rica international spent the 2013/14 season on loan with Olympiakos so knows what sort of reception to expect but still feels Arsenal are well-equipped to come away with a memorable victory.
"We got the result (against Sunderland) and that's what we wanted, now we have to prepare mentally and physically for Wednesday's game because it will be very difficult," he told the IBTimes UK.
"We already played against Olympiakos at Emirates Stadium. They are a great team, a great rival and especially because they play at home.
"In the Pireo (Karaiskakis Stadium) it is very difficult to get points, but it is the last game of the group stage and we will give our best.
"It is the most important game of the season so far. It will be a cup final and we have to win to continue in the Champions League."