"The first match of the World Cup is always crucial. I worry about which team will score the opener... The team know how to achieve our goal. I have no issue with that. Balance matters most, if we want to make substitutions during the game, we need to focus on the distinctive features of the rival [Serbia], take their weak spots into consideration," Ramirez told journalists.

Costa Rica will face Serbia in their first World Cup match in Samara on Sunday.

"Tomorrow there will be a new page in history, and we know how to play in the group. The main thing is to win tomorrow. I think that we have the opportunity to defeat Brazil, but now we need to think about tomorrow," Ramirez added.

The games of the 2018 FIFA World Cup will be held at 12 stadiums across 11 Russian cities till July 15.

Costa Rica will play five-time World Cup champions Brazil, Serbia and Switzerland in Group E.