Teenager Fati showed pace and anticipation to nip in between two Celta defenders and fire Barca ahead in the 11th minute, picking up where he left off with his two early goals in Sunday’s 4-0 win over Villarreal.
Barca’s lead looked to be under threat when Lenglet received a second booking at the end of the first half for striking former Barca player Denis Suarez in the face, sparking furious protests from Messi and Gerard Pique.
But Barca quickly doubled their advantage soon after the interval, as Messi tore through Celta’s defence and fired a low shot which took a heavy deflection off Lucas Olaza and squirmed past keeper Ivan Villar for an own goal.
The Catalans, who had failed to win their last five league games at Celta’s Balaidos, maintained control even with 10 men, only once looking in danger of conceding.