The Ligue 1 side have been struggling to find their best form this season and lost star striker Olivier Giroud to Arsenal in the summer transfer window.
|EXPERTS DEBATE CL CONTENDERS
|Carlo Garganese, James Goldman and Peter Staunton run the rule over the teams vying for the famous trophy
"Montpellier showed last season that a cohesive unit can go a long way. They surely should not be underestimated: you don't become French champions for nothing," the Schalke boss said at a press conference.
"Whether or not they have stars in their ranks it doesn't really matter – they have some very good players.
"They have really good attacking players, and the fact that people in Germany don't always know them is par for the course.
"Right from the beginning I said that Arsenal are the group favourites and that Olympiacos, Montpellier and Schalke will battle for second place. That's still the case."
Wednesday's encounter at the Veltins Arena kicks off at 20:45CET.