The in-form striker was quick to play down the significance of his side's shock defeat by Real Sociedad, while Pedro attributed the loss to Gerard Pique's sending-off
Despite bagging a goal in his 10th straight league game in consecutive seasons, Philippe Montanier's men staged an incredible comeback to stun Messi and the Blaugrana.
But the newly-crowned Balon d'Or winner told reporters: "Losing a game had to come at some point.
"We have to pick ourselves up immediately because of the cup match coming up.
Meanwhile Pedro, who scored Barca's other goal, was quick to blame the defeat on the referee's decision to produce a second yellow-card for Gerard Pique.
"Pique’s red card conditioned the match, because it was a [tackle] that wasn't dangerous. On Thursday, we simply cannot fail," he said.
The Camp Nou outfit travel to Malaga in midweek for their Copa del Rey quarter-final.