Ahead of the opening leg in the San Siro, the majority of pundits and bookmakers have made Barca the favourites to progress through to the quarter-finals of the competition.
Despite admitting that his team are the "underdogs", French defender Mexes has insisted that he expects the Rossoneri to attack their Spanish opponents.
"I think it will be open until the end. We are the underdogs but we believe in ourselves," he told UEFA's official website. "Although the team is pretty young compared with last year, and now it's a different Milan. We are still Milan and we will go for it."
When the two sides met last season, Barca ran out 3-1 winners on aggregate.