Referee Yuichi Nishimura had a tough day at the office during Brazil's victory over Croatia. 

After an opening weekend of curious calls and blown decisions, fans are rightly wondering just how these referees got to the World Cup.

Controversial verdicts marred each of the first three matches; Japanese referee Yuichi Nishimura marred the opening game between Brazil and Croatia by awarding a suspect penalty to the home side in the second half and wiping away a potential Croatian equalizer with minimal reason to do so; Giovani dos Santos saw two valid goals scrapped by incorrect offside decisions in the first half of Mexico’s 1-0 victory over Cameroon; and Diego Costa won a penalty in the 2010 World Cup final rematch between Spain and the Netherlands by stepping on the back of Stefan de Vrij’s leg and tumbling to the ground.

Each of those decisions drew wide disapproval from viewers at home and prompted the usual laments about the standard of refereeing. But if FIFA assembled many of the top referees in the world for this tournament, then why are they struggling so mightily to make the correct choices?

And let’s make this clear: FIFA did carefully evaluate referees from across the world and selected the very best of those candidates to comprise its pool for the World Cup. The officials boast top-level experience in their native confederations and countries and pass rigorous fitness tests in order to confirm their physical suitability for the grandest stage.  They are -- by and large -- some of most qualified people on the planet to make decisions in World Cup matches. They get most of them right, but they also often get some of the major decisions wrong. It happens in every World Cup.