The 58-year-old coach insists his side's defeat last Saturday will not distract them from the task at hand as they aim for a spot in the knockout phase of the competition
The Gelsenkirchen side sit atop of Group B with eight points from four games, and will qualify for the knockout stage with a win over the Greek champions.
"The Bundesliga defeat by Leverkusen is in the past. We are focused on the goal before our eyes, to qualify for the next round of the Champions League," Stevens said at a press conference.
"Olympiakos are playing well in the Greek Super League and are a successful side. They have also won their past two games in the Champions League, so that tells you something.
"It will be about showing our qualities and trying to make it as difficult as possible for them. We are at home and we hope to achieve our aim with the help of our fans."
Stevens' side recorded a 2-1 win in Greece in September's reverse fixture.