Lionel Messi's Argentina will be closely watching the 4pm kick-off between Nigeria and Iceland.
A Seleção controlled the game from start to finish, averaging two-thirds of possession while largely camped in the Costa Rican half.
It's Brazil who take centre stage today as they open up proceedings at 13:00 and Paul Robinson believes that they will fare better than their South American rivals did last night.
Neymar could be a doubt for Brazil's Group E clash against Costa Rica on Friday after he limped out of a training session with what appeared to be a foot complaint on Tuesday. "We want to win but the coach is not going to play around with a player's health, the price would be too high to pay".More news: Melania Trump wears ‘I really don’t care’ jacket to visit DETAINED children
It was a free kick from Kolarov that put Serbia in solid position in the group, but Switzerland may be as tough a foe as Brazil.
They face Costa Rica in St Petersburg needing a win after a disappointing 1-1 draw with Switzerland in their opening game.
Switzerland used a strong defence and midfield to stifle Brazil, and midfielder Valon Behrami made the match very hard for Neymar. An off-colour Brazil needed dramatic late goals by Philippe Coutinho and Neymar to earn their first win of the World Cup and go to the top of Group E with four points.
Serbia, meanwhile, is seeking to reach the round of 16 for the first time since 1998, when it was known as Yugoslavia.