Alejandro Sabella believes Lionel Messi's habit of throwing up on the pitch is due to anxiety.

“Nerves. I reckon that in these moments there is anxiety more than anything,” Sabella said before the team departed for Brazil. “It’s difficult to remain calm.”

After Messi threw up less than 10 minutes into a friendly match between Argentina and Romania in March, his then coach at Barcelona, Gerardo Martino, said “something is not right”, though he added that it was not affecting Messi’s play.

Messi was seen dry-heaving in Saturday's match against Slovenia, but he scored just four minutes later.

Barcelona’s medical staff have not been able to find the cause. Neither have Argentina’s team doctors, nor Messi himself. Messi says it is just something that happens to him in training, during matches and even when he’s at home.

“I don’t know what it is. But I had a thousand exams,” Messi told the Argentinian broadcaster TyC Sports earlier this year. “I start to feel nauseous to the point where I almost vomit, and then it goes away.”