Vasiljevic was left in awe of the Argentine superstar, after his match-winning brace against Real Madrid last Sunday.
He has however called on his players to show no fear against the La Liga champions.
“I’ve already said that we need a plan for Messi and the players told me [that we need to] carry handcuffs and a pistol,” he told a news conference.
“He disconnects, but later he plugs [himself] in for 10 minutes and does what he does.”
Osasuna know that defeat to Barcelona could see them all but relegated.
Barca have just five games left to play and will be without the suspended Neymar on Wednesday, who misses the final game of his suspension following his red card against Malaga.