The injured Austrian is confident his team-mates can overturn their deficit to Barcelona, while Medhi Benatia insists they must believe they can go through.
The Uruguay international struck for the seventh time in four Ligue 1 games, while Zlatan Ibrahimovic netted two goals and made another for Maxwell with an exquisite chip.
The Barcelona star sent Twitter into meltdown on Wednesday with his match-winning performance against Bayern Munich at Camp Nou.
The Bavarians were back to their imperious best on Saturday as they took apart the visitors in the first half, with both goals coming inside the opening 45 minutes.
Javier Pastore helped inspire Paris Saint-Germain to a 3-1 victory over Metz on Tuesday night as the reigning Ligue 1 champions moved two points clear at the top of the division.
The visitors had hoped to fire a statement of their ambitions but were comprehensively dismantled at Allianz Arena by an imperious Bavarian showing before the break.
Tim Sherwood's men fought back from a goal down to book a meeting with Arsenal in the showpiece at Wembley, despite the Reds taking the lead on Sunday afternoon.