Barcelona failed to score for the first time in 46 home games as they were held to a draw by Slavia Prague.
Lionel Messi, who did not score or provide an assist for the first time in a home Champions League group game since 2012, struck the bar and had the best of Barca's six shots on target.
His fierce left-footed strike was well saved by Ondrej Kolar in the first half.
Barca remain top of Champions League Group F, while the visitors are bottom.
Ernesto Valverde's side have eight points from four games, while Borussia Dortmund are in second spot with seven points after beating Inter Milan in a thriller at the Westfalenstadion.
The visitors started brightly but the exciting Nigerian striker Peter Olayinka was unable to latch onto Petr Sevcik's square pass in the fourth minute.
Barca were lacklustre early on and their most potent attacking threat was full-back Nelson Semedo, who twice broke clear down the right, before wasting the final ball.
Messi then grew into the game, showing glimpses of his brilliance without being able to strike the decisive blow.
The Barca talisman brilliantly turned Michal Frydrych in his own half before bursting clear and firing a shot at goal, but his effort struck the crossbar.
Moments later, Kolar was on hand to keep out a Gerard Pique header with another acrobatic save.
Both sides had goals disallowed for offside after the video assistant referee (VAR) intervened, as first Jan Boril's close-range finish was ruled out, and then Arturo Vidal's finish was chalked off after Messi was penalised in the build-up.
Winger Ansu Fati, 17, was introduced off the bench in the second half and he quickly fed Messi with the outside of his right foot, but the Argentine could only direct his shot straight at the excellent Kolar from close range.
Barcelona lost 3-1 to Levante in La Liga on Saturday and coach Ernesto Valverde said: "We haven't been convincing, either on Saturday or today, and we know there is a lot of pressure now on the team. We have to respond."
The La Liga champions face Borussia Dortmund at home in their next Champions League game on Wednesday, 27 November (20:00 GMT), while Slavia host Inter Milan at the same time.