The 23-year-old Frenchman went in to tackle Pere Pons of Girona in the 33rd minute, and appeared to win the ball fairly at first glance.
However, the Girona player went down clutching his face, which was enough to trigger a VAR review by the officials.
On viewing the replay, it appeared as though Lenglet raised his elbow into an unusually high position, striking the opposing player flush in the face.
The referee decided that he had no choice but to dismiss the defender, prompting furious reactions from his teammates.
Barcelona had been 1-0 up at the time, but conceded an equaliser on the stroke of half-time to make it 1-1.
September 23, 2018