Neymar was initially in the middle trying to regain possession of the ball but as soon as he made a block with his right foot, he grimaced in pain.
It's believed the issue is related to his ankle, the same ankle he was favouring after taking more than one whack in that area during the course of the game against Switzerland.
A battered and bruised Neymar will aim to get Brazil's World Cup campaign back on track here Friday as the pre-tournament favourites seek to re-assert their title credentials with victory over Costa Rica.
Team-mate Philippe Coutinho, who scored Brazil's stunning goal against Switzerland, confirmed Neymar felt pain in his ankle but played down the injury.
Alexi Lalas took vocal exception to the treatment, which resulted in three yellow cards for the Swiss. Of course, others thought that Neymar milked the contact for all it was worth, falling to the ground often.More news: Hawks eyeing Luka Doncic with the No. 3 pick
Accompanied by a physio, Neymar couldn't keep up with the pace of his teammates and so had to abandon training early.
"Neymar was a complete disaster", he said (via Marca)."He did not have an acceptable game and should have been substituted". There was fun poked at the performance of the big teams.
"Because of the number of fouls he suffered in the last match his ankle is a little painful, but he will train normally tomorrow".
"If everyone does his job, then the team grows and plays well". Mexico's win will now further boost hopes of getting past the last-16, which has proved to be their bogey round in the last six World Cups.