Rangers stunned Borussia Dortmund 4-2 in the Europa League on Thursday while Barcelona had to come from behind to draw 1-1 at home to Napoli in their play-off first leg tie.
Napoli gained a 1-1 draw in Barcelona.
The visitors, challenging for the Serie A title, opened the scoring in the Nou Camp against a home team that is scrambling just to finish in the top four in La Liga.
Polish midfielder Piotr Zielinski ran onto his own rebound to slam the ball home after 29 minutes.
Barcelona increasingly dominated possession but needed one of four penalties awarded for handball by VAR in the Europa League on Thursday to level.
Adama Traore's cross hit Juan Jesus on the arm after 59 minutes.
Ferran Torres converted the penalty with confidence for his first goal at Camp Nou for Barcelona but his cool deserted him as he hit two good chances over the bar as Barcelona dominated the closing stages.
