It was caught by an Italian TV broadcaster, and confirmed by the Associated Press.
This happens to Messi with some regularity. In April cameras captured the 26-year-old retching in the tunnel before a game against Athletic Bilbao. That came a little more than a month after he threw up during an Argentina friendly against Romania in Bucharest.
That incident prompted a wave of media inquiries into what's going on with his stomach. While Messi, his coaches, and his doctors have thrown out a bunch of different theories, there isn't one clear explanation.
Barcelona coach Gerardo Martino told the BBC back in March that Messi went to a doctor, but the tests didn't reveal anything:
"Something is not right, but it doesn't affect his performance. It happens to him regularly. ... He has even gone to see specialists at certain times but their tests have proved inconclusive."
Argentina's team doctor told Marca that it's nothing to worry about, and listed a bunch of possible explanations:
"One cause can be physical and/or mental strain. The change in time zones - jet lag - and changes in diet also take a toll. Sometimes when people change their eating habits, it can trigger intolerance, leading to nausea and vomiting."
Messi himself called it "no big deal," saying, "Sometimes I accelerate very fast and the change in air intake causes me to heave. I felt completely fine at the end of the match"
It appears to be a strange but harmless ailment, but it happens all the time.
Against Atletico Bilbao in April:
Against Romania in March of 2014:
He also got sick against Levante in August of 2013 and Bolivia in March of 2013, as well as a Super Cup game against Real Madrid in 2011:
In the World Cup final:
