Aritz Aduriz is not yet celebrating after his hat trick helped Athletic Bilbao to a 4-0 win over Barcelona in the first leg of the Spanish Super Cup on Friday.
The European champions stumbled out of the block, but Aduriz said Barcelona are capable of overturning the result in the second leg at the Camp Nou on Monday.
"We're very pleased, but we know how difficult it is to win at Barcelona," he said after the game. "Coming back from 4-0 down is almost impossible, but the second leg will still be very difficult.
"If we win the trophy on Monday then tonight may be the happiest night I've ever had with Athletic.
"But we can't think that a four-goal advantage will be enough at Barca's ground."
Aduriz, who recorded a hat trick in 15-minute span at San Mames, said Athletic can came away with the trophy as long as they stick to their strategy.
"All of the goals have been important and satisfying. Out on the pitch, we just try to continue with the same willingness and determination," he said.
"We have to be ourselves, do what we have been doing and try to score at least one goal. We will also need to be strong at the back so that Barca struggle to score."