The Real Madrid defender rated the Barcelona star even higher than Cristiano Ronaldo, while alerting his Selecao team-mates to the threat posed by Argentina
The Selecao will tackle Argentina on Saturday and will be looking to bounce back from Sunday's 2-0 defeat against Mexico, which ended a run of eight consecutive victories.
Despite meeting Messi several times throughout the season at club level, Marcelo says there is always a special feeling to locking horns with the Barcelona star - whom he rated higher than his Real Madrid team-mate Cristiano Ronaldo.
"Right now, Messi is the best player in the world and it is a pleasure to play against him," Marcelo told Globoesporte.
"We will see what happens, if we can mark him. Argentina are more attacking [than Mexico], so we will have space to play.
"But we need to be careful, because they can score goals easily. You cannot talk about one or two players only, but about their entire team.
"But we also have several good players and we will try to secure a good result."