The Catalans have done their best this season to forget about the cup, convinced their deep runs and eventual triumphs over the past four seasons have hurt them in the Champions League.
But with two upcoming cup Clasicos thrown into their path, the Blaugrana finally caved, resting players against Valencia in La Liga on Saturday, and they stumbled to a 2-2 draw.
It extends their lead at the top of the table to six points, but both second-placed Atletico Madrid and Real Madrid in third can close the gap on them when they play against Real Betis and Alaves, respectively, on Sunday.
Ernesto Valverde rested midfield passing machine Arthur, opting for Arturo Vidal, even though Sergio Busquets was suspended too.
The coach also played Sergi Roberto at left-back instead of Jordi Alba, who is having a sublime season, and Thomas Vermaelen next to Gerard Pique, resting Clement Lenglet.
Valencia took advantage. The visitors broke the deadlock in controversial fashion, with Messi appearing to be felled at one end before Los Che raced down to the other, Rodrigo leading the charge.
The Spain striker, who hit a cup hat-trick against Getafe to put Valencia in the semi-finals themselves, slipped in Gameiro who finished coolly past Marc-Andre ter Stegen.
Busquets’ suspension gave Valverde little choice but to deploy Ivan Rakitic in the holding role, and if the Spaniard was there he might have done more to stop the break.
More preventable still was Valencia’s second goal, with Sergi Roberto out of position at left-back and out of position in the moment too, shoving over Daniel Wass to stop him reaching a cross. Valencia skipper Dani Parejo slammed home the penalty to give his team a commanding advantage at Camp Nou.
However, when you have Messi on your team you always have a chance, and the Argentine star pulled one back from the penalty spot after Lato fouled Nelson Semedo.
It was Messi’s 20th league goal of the season and the ninth consecutive match in which he’s found the net, across all competitions.
The 21st followed after the break, another Messi special – a shot most players wouldn’t have attempted – that left goalkeeper Neto unsighted as it whistled into the bottom corner. With a thicket of players in his way, the shot wasn’t on, until suddenly it was, and the ball was already spinning in the back of the net.
Alba was thrown on by Valverde at half-time, with the coach looking for fruit from the special connection the defender shares with Messi, while Coutinho was taken off as the team chased a winner. It was another disappointing night for the Brazilian.