Costa Rica: The Central American side has no reported injuries going into the encounter but due to poor friendly results, their starting XI is more of a guessing game than an exact science.
Joel Campell, Bryan Ruiz, Christian Bolanos and Johan Venegas are competing for two positions on either flank.
Serbia: The European side also have a full contingent of players to choose from and have some real stars among their squad.
Wonderkid Sergej Milinkovic-Savic will be key for Serbia but the midfielder is expected to play a deeper role alongside Nemanja Matic, while Dusan Tadic and Aleksandar Mitrovic will be expected to carry the weight of scoring goals.
Costa Rica defender Giancarlo Gonzalez about springing another suprise:
"We've waited on this moment for a long time and we need to implement what we've practiced. A lot has been talked about regarding the last World Cup. This is a new World Cup, a new story. Some of us are back, we know the eyes of the world are upon us.
"We have prepared ourselves and we'll do everything we can to play well tomorrow because this team represents our country. We'll try to find victory, which is what we've been working for."
Serbia coach Mladen Krstajic on his side's chances of qualifying:
"Of course the upcoming game is the most important in several years. Tomorrow's game will show how important the subsequent games will be. Whatever the score, whatever the result, Switzerland is going to be the key for our qualification.
"I hope that we will get a good result and it will mean a lot to us if we do win tomorrow."
Did you know?
Sunday's clash will mark the first encounter between the two countries held on neutral ground.
Prediction: 1-1
Possible lineups:
Costa Rica: Navas, Oviedo, Duarte, Acosta, Gonzalez, Gamboa, Campbell, Guzman, Borges, Ruiz, Urena.
Serbia: Stojkovic, Kolarov, Tosic, Milenkovic, Ivanovic, Matic, Milinkovic-Savic, Kostic, Ljajic, Tadic, Mitrovic.