Messi has fallen below his own exceptionally high standards over recent weeks, drawing a blank in three of his last four games.
He did, however, score a hat-trick when Barca last met Real Madrid and Laudrup has backed the Argentina international to strike another blow against their Clasico rivals in the Copa final.
"It's very complicated when you speak about him," he told Spanish radio station La Xarxa.
"He's the best in the world and one of the all-time greats. We've been spoilt.
"In recent games, he hasn't been at his best but people also said that before (March's) Clasico and he scored three goals and created another."
Messi's apparent downturn in form has coincided with a tough patch for Barca, who were eliminated from the UEFA Champions League before falling further off the pace in La Liga with defeat to Granada.
With Gerardo Martino's best chance to win silverware this season coming on Wednesday, the former Swansea City manager offered the current Barca boss his support.
"When things aren't going well it's very easy to blame the coaching staff," he explained.
"It's easier to change the manager than all the players. It's never easy to choose who should be in the dugout."
