Vlaar warns Costa Rica of Dutch confidence
Louis van Gaal's men have won all four of their matches at the tournament in Brazil, including a 5-1 demolition of holders Spain in their opening fixture.
Netherlands were further boosted by a late rally against Mexico in their last-16 tie, with late goals from Wesley Sneijder and Klaas-Jan Huntelaar ensuring a dramatic 2-1 triumph.
The reward for coming through that contest is a last-eight clash with surprise package Costa Rica, who progressed via a penalty shoot-out victory over Greece.
Vlaar is confident of reaching the semi-finals because of the high spirit among the Dutch squad.
"The mood in camp is great," he told Aston Villa's official website.
"It's been brilliant so far. We have won all of our games so it's so far, so good.
"I am really looking forward to the game on Saturday. It's another great challenge - another good game against good opposition - and we want to get through.
"Results help, of course, especially when you beat the world champions [Spain] 5-1. We are really focused. We are training very hard. The feeling in the group is very good.
"Everyone is together - we are all in it together. You can see that in the games."
Netherlands will begin the match in Salvador as favourites, but Vlaar warned his team-mates not to be complacent against a side who beat Uruguay and Italy in the group stage.
"These games don't come easier," he added.
"There are no easy games.
"Costa Rica beat Uruguay and Italy and then drew against England. Then they beat Greece.
"It will be another hard game again - but we are really looking forward to it. It's a great challenge again."