The Roma midfielder helped the Italians get off to a winning start against England in Group D but face a dangerous Costa Rica outfit who also took maximum points in their opener.
In a surprise result, they came from a goal down to beat Uruguay 3-1, hugely boosting their hopes of securing progression to the knockout stages for the first time since 1990.
Following that victory, De Rossi wants to ensure Italy treat Costa Rica with respect as they look to all but confirm their own last-16 spot.
"We should fear them a bit. You need a healthy fear against a team that surprised everyone with their victory over Uruguay," he said.
"Nobody thought they would get such a clear result against a very strong side.
"They'll be fired up after that win. If they had lost 4-0 then we could've underestimated them, but in this case we cannot possibly do that.
"I hope, and am convinced, that we can virtually secure qualification by beating Costa Rica. A victory would put a strong stamp on our ticket to the next round."
