A suspected broken ankle to Aleix Vidal soured an otherwise perfect afternoon for Barcelona as four goals in eight second-half minutes helped them on their way to a 6-0 victory over Alaves.
After looking organised in the opening half hour, Alaves went behind eight minutes before the break when Luis Suarez - banned for the Copa del Rey final - slotted in Vidal's cross.
Los Cules added to their tally just three minutes later, when Fernando Pacheco's mistake gifted Neymar the second.
Both sides looked sharp as the second half began, but Lionel Messi ensured each of the 'MSN' trio found themselves on the scoresheet when he robbed Carlos Vigaray and slammed home from a tight angle (49).
Alexis turned the ball into his net under pressure from the Argentine to make it four (63), before a goal from Ivan Rakitic (65) and a second from Suarez minutes later completed the rout (67).
Vidal was stretchered off inside the final 10 minutes after feeling the effects of a robust challenge from Theo Hernandez.
Last season's Segunda Division champions had caused an upset at Camp Nou back in September as they defeated Luis Enrique's side 2-1 - just one of two league reverses suffered by Barcelona this season - and came into the game buoyed by a midweek victory over Celta Vigo that secured a first Copa Del Rey final berth in the club's 96-year history.
Mauricio Pellegrino's men began the game well, keeping their opponents at bay for large spells, restricting them to half chances and playing on the counter.
They had the first opportunity that sparked the game into life after 26 minutes. Left-back Hernandez broke down the left and advanced towards Marc Andre Ter Stegen's goal, but his powerful effort was well kept out by the German stopper.
Almost immediately at the other end, Andre Gomes had a similar chance that Pacheco turned behind and then within minutes, Los Cules found the vital opening. Vidal, in acres of space on the right flank, spotted Suarez in the centre of the six-yard box. The Uruguayan evaded the challenge of Alexis and slotted the cross home.
Three minutes later, Neymar doubled the lead. Pacheco couldn't quite get enough power to take Messi's swerving ball away from the advancing Suarez. His clearance only aided the goal as he pushed the ball onto Suarez's head and onto Neymar who struck home.
As the second half began, both sides threatened, with Alaves not keen on letting Barca walk all over them. They had the first chance as Nenad Krsticic's attack was ended by Lucas Digne on the edge of the box.
Minutes later, Messi grabbed the third, robbing the ball from Carlos Vigaray's feet and hitting a smart finish past Pacheco from an acute angle.
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Four minutes later, it was four when Alexis turned Suarez's cross - bound for Messi - into his own net and then Rakitic converted Suarez's intuitive backheel for five.
Still Alaves continued to battle, but Suarez capped the victory and a totally-dominant eight-minute period when he slammed home after Neymar's shot was blocked.
The home fans impressed right until the final whistle, but were temporarily halted when Vidal's injury sent shockwaves around the Mendizorrotza. Hernandez's lunging - but fair - challenge caught Vidal off-guard and left him with a sickening ankle injury that will no doubt keep him out for some time.