Costa Rica qualified for their second consecutive World Cup and qualifying included their first ever win in the United States so morale is high and they will be motivated to cause one or two upsets as they did four years ago.
The squad has plenty of experience within the camp and with Real Madrid goalkeeper Keylor Navas in the team, he will be key in marshalling a defence and team that we can expect to be well organised and cohesive.
The lack of playing time for some of their important forward players like Ruiz and Campbell could be an issue, but they will be raring to go here and in some ways that may play into their favour as fatigue will certainly not be an issue.
Predicted line-up (5-3-2):
Gamboa, Acosta, Waston, Duarte, Oviedo
Borges, Bolanos, Tejeda
Serbia topped a difficult group in qualifying but they still decided to sack coach Slavoljub Muslin and replace him with Mladen Krstajic who comes in with the mission to make the team a more appealing and attacking outfit.
Milenkovic could be a starter in defence and the talented Milinkovic-Savic could easily get the nod too in midfield, and the former would help bring some youth to what is a relatively ageing defence.
On paper there is plenty of quality in this squad but they remain psychologically fragile and things could turn sour if and when things do not go well, and similar to a couple of other teams, it seems highly improbable that they will be able to fundamentally change their way of playing so soon before the tournament and to be successful with it.
Predicted line-up (4-2-3-1):
Rukavina, Ivanovic, Tosic, Kolarov
Tadic, Ljajic, Kostic
The fight for second place in this group behind Brazil really looks to be a tight one and neither of these sides will want to lose this opener that will make it virtually impossible to recover from. That may see them both approach this quite cautiously and they are not helped by the fact that neither possess a great deal of firepower. The Serbs are one of the more temperamental teams in the tournament so their matches could easily ignite at any stage, but even still, it seems unlikely there will be many goals in this one.