Robert Lewandowski warmed up for next week's meeting with his former club by scoring a hat-trick in Barcelona's demolition of Viktoria Plzen.
The Poland forward made it eight goals in five games since he left the German team.
It was his first appearance in the competition for Barcelona and he scored a clinical finish to double the lead.
He scored on the stroke of half-time after Ousmane Dembele did well to win back possession.
The travelling fans from the Cech Republic got something to cheer when Jan Sykora headed past ter Stegen, but the strength of the two teams proved too much.
After an assist by a former Manchester City player, Lewandowski completed his hat- trick.
He demonstrated his class tonight. He is one of the best forwards in the world.
It is the first time that a player has scored a hat-trick for three different teams in the same European competition.
He has scored at least one goal in his last 20 matches.
The perfect start was made by Barcelona, who face the winner of the Inter Milan-Bayern game on Tuesday.
In his first season with the club, he scored 50 goals in 46 games to help them win their 10th straight title.