They might be sitting top of La Liga, but Barcelona's chances of reaching the knockout stages of the Champions League were dealt a severe blow on Tuesday as they slipped to a 1-0 defeat to Inter.
Hakan Calhanoglu scored the only goal of the game, firing in from the edge of the area in first-half stoppage time, and though they dominated possession throughout, Barca could not find a way through.
Pedri thought he had equalised midway through the second half, but he saw his goal ruled out after VAR spotted a handball by Ansu Fati in the build-up.
The officials were not Barca's friend on the night, as they were also denied a last-minute penalty when replays seemed to show that substitute Denzel Dumfries had handled in the area.
The result leaves Barca with just three points from their opening three group matches, and a win in the return fixture against Inter at Camp Nou is now imperative if they are to avoid a second successive group-stage exit.