Time is now for Neymar to show he can handle the heavy lifting with Brazil

The keys of Rio de Janeiro have been handed to King Momo, who has promised to rule for the next few days with no regard for decorum.

The world's biggest carnival has kicked off. All over the city there are informal street parties -- and the centrepiece is the purpose-built sambadrome, where over the next few nights the working-class organisations known as samba schools are putting on the parade.

It is all fiercely competitive. There is promotion and relegation, there is a title at stake and there is always controversy about the judging. The results are read out with all due deliberation and solemnity on Wednesday afternoon -- and this year this will happen a little bit earlier than usual. The reason? Once it is over and done with and the winner has been declared, then Brazil can sit down to enjoy Paris Saint-Germain's trip to Spain to face Real Madrid in the Champions League. It is not only the samba schools waiting for the verdict; judgment time is now approaching for Neymar.

When the Brazilian star swapped Barcelona for PSG back in the summer, the objective was clear: After spending time in the refreshing shadow of Lionel Messi, the moment had come to search for his own light. He wanted to be the main man in the orchestra.

So far, so good. The world of football has benefited from having another team that everyone wants to see. Barcelona have not suffered too much from his loss. PSG have gained considerably from his acquisition. But, so far, little of real relevance has happened. Because Neymar was never going to be judged on his performances in the domestic French league, or in the group phase of the Champions League.

The moment of truth has arrived, and will stretch out in the next five months. How will he perform at the business end of the Champions League? And can he dominate Russia 2018? At the age of 26, this year's World Cup is almost certainly the one that he will play closest to his physical peak.

The criteria used to asses Neymar will be rigorous. This is the situation he has chosen. Can he now prove capable of living up to the extent of his own ambition? And given his undeniable technical genius, the answers may mainly lie in the force of his mental strength.

As a general rule, to play well is to choose well. Flicks and tricks can produce goals -- if they are used at the right time, and they circulate the ball well and open up space in the opposing defence. Neymar is not only gifted with spectacular ball skills, he is also extraordinarily mentally sharp. Like Jake LaMotta in "Raging Bull", there are times when he appears to be seeing things in slow motion. While his marker is overwhelmed by the speed of his movement, he seems to have plenty of time to decide what he wants to do. This means that he has plenty of options. The question now is this: under pressure, will he choose the best ones? Or will his thought process be distorted by his own perceived necessity to live up to the expectations and shine individually?

This promises to be one of the most fascinating questions swirling around world football over the next few months.

He can get the balance wrong. Playing for Brazil against England recently he showed some magnificent skills and acceleration -- but, too eager to do something special at Wembley, his choice of options was poor. There were plenty of wild 30-yard shots when a pass followed by a burst into space would have served better. At home to Ecuador in a World Cup qualifier a few months earlier, he played a dreadful first half; overly concerned with drawing fouls in midfield, he was responsible for the temperature of the game rising to a dangerous level -- in which he lost his head and picked up a yellow card for a wild tackle. These are the kind of lapses that can prove very expensive at the highest level.

But if he gets the balance right, then the world will have a fitting heir to the throne shared for so long by Messi and Cristiano Ronaldo. Let the carnival begin!