Uruguay, England and Italy are expected to do battle for the top-two spots in the group, with Costa Rica tipped to make an early exit from Brazil.
But speaking on the eve of Saturday's clash at the Estadio Governador Placido in Fortaleza, Muslera says Costa Rica have enough talent at their disposal to cause problems.
"Of course it's a very important game, but we don't see Costa Rica as the easiest team to play in the group," the Galatasaray goalkeeper told reporters.
"We have respect for Costa Rica as we have for all countries, all teams we have faced.
"We already have taken all the precautions. We know them (Costa Rican players), they are playing in European leagues.
"We know their characteristics of speed, of good shots from outside the box, they are players to be aware of when they counter-attack.
"So we'll try to be ready to respond and try to stop them get to the ball."
Uruguay will be without Luis Suarez for the match after coach Oscar Tabarez confirmed the star striker would not be risked as he continues his recovery from a knee injury.
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