Brazil legend Kaka has given his thoughts on why we have not seen the best of FC Barcelona superstar Lionel Messi at the 2018 FIFA World Cup so far.

The 31-year-old, who is regarded as one of the best players in the history of the game, missed a penalty in Argentina's draw with Iceland and failed to have any impact in the Albiceleste's 3-0 loss to Croatia.

Messi, who is yet to score in Russia, has been the subject of a lot of criticism in recent days, but Kaka believes his critics should take a look at the bigger picture.

‘Messi is going through a difficult period with Argentina, and this shows the importance of the group in soccer,’ the former Real Madrid midfielder said, as quoted by ESPN.

‘He is someone who strengthens those around him, but when it's not working, he also starts to struggle.

‘It's quite surprising that against Nigeria, this struggling Argentina side could still qualify, but we'll see what happens.’

The South American side, currently last in Group D, need to beat the Super Eagles and then hope Croatia beat Iceland if they are to have any possibility of qualifying for the competition's round of 16.