The Ticos have been one of the surprise packages in Brazil, topping Group D by pulling off upset wins over Uruguay and Italy before a 0-0 draw with England clinched the top spot in a group that Greece head coach Fernando Santos labeled the "Group of Death."
Most observers felt that Costa Rica was the clear outsider in a group that contained three former World Cup winners. But the CONCACAF representatives used a high-pressure style to unsettle both Uruguay and Italy, and Greek boss Santos knows his side must be ready for a tough task.
"I am delighted first of all that we bring joy to the Greek people," said Santos after his team secured a place in the knockout round for the first time in the nation's history. "We have time to think about the match with Costa Rica. We will go back to our base, think about it and study our opponents. We have to pay a lot of attention to this game, they came out top in the 'Group of Death'. As a result we cannot allow ourselves to underestimate them."
The path Greece took to get to the last 16 was much different than the one the Ticos traveled as the Greeks lost their opening match 3-0 to Colombia.
A 0-0 draw with Japan that saw Greece play the final 52 minutes with 10 men kept the team alive, but Santos and his side saved their best performance for last, notching a 2-1 win over Ivory Coast as Georgios Samaras converted a stoppage-time penalty kick to send his side through.
The result was certainly a surprise to many, including Costa Rica midfielder Yeltsin Tejeda.
"They are in the World Cup and they beat an excellent team, Ivory Coast," Tejeda said of Greece. "If they are there (in the Round of 16), it is because they were better."
"We were thinking more about Colombia and the Ivory Coast and in the end came the least expected team. Now we have to change the video cassette."
Costa Rica will certainly have to prepare much differently for Greece than for either Colombia or Ivory Coast if the team is going to reach the quarterfinals at a World Cup for the first time.
Greece is known for a being a defense-first side that looks to steal a goal or two in order to win ugly.
But Costa Rica's defense has been one of the best at the tournament, giving up just one goal in three games, which came on a penalty kick against Uruguay in its opening match.
The winner of this contest will be in uncharted territory, while a Greece victory would bring about an interesting situation involving Santos.
With his contract set to expire the day after the Costa Rica match, the 59- year-old may need to negotiate a quick extension if his side reaches the last eight, which is yet another indication of how unlikely a matchup this is at this stage of the tournament.