BBC Sport - Lionel Messi says he was brought to tears after scoring the opening goal in Argentina's 3-0 win against Algeria because of a matter "completely unrelated to football".
The Argentina captain claimed a magnificent hat-trick on his 200th appearance for his country as his side made the perfect start to their World Cup defence.
After curling home a wonderful opener after 18 minutes, the 38-year-old was swarmed by team-mates in celebration before being spotted wiping away tears on his shirt.
"Why did I cry? It was something completely unrelated to football," said Messi.
"I went through some difficult days, but I'm grateful to the entire delegation and my team-mates because they were always by my side, giving me a lot of strength to help me get through it."
Messi's hat-trick, which was his first at a World Cup, took his finals goal tally to 16, moving him level with Germany's Miroslav Klose as the all-time leading scorer in the competition's history.
Messi also became the first player in history to feature at six World Cups, 20 years to the day since his debut at the tournament, where he scored in a 6-0 win over Serbia and Montenegro.
The eight-time Ballon d'Or winner's performance helped Argentina win their opening match at a World Cup as defending champions for the first time, after defeats in 1982 and 1990.
Messi's record-breaking performance followed doubts about his fitness after he was substituted early due to muscle fatigue last month in his last MLS match with Inter Miami before the World Cup.
"It makes me very happy to have lived through everything that came my way," Messi added.
"What I'm living through now is the cherry on top. I'm very happy and grateful for this wonderful group, I enjoy it so much."
Messi was substituted after 80 minutes against Algeria to a standing ovation as his name echoed around the Kansas City Stadium.
Messi inspired Argentina to World Cup glory in Qatar in 2022 to win the one trophy which had long eluded him, and he will be essential to Argentina's hopes of becoming only the third nation to defend the trophy.
"There are no words to describe him. If anyone thought this team was better without Leo, today it was proven that the opposite is true," said Argentina midfielder Alexis Mac Allister.
"He is our most important player. We need to build a team around him, and we are doing it."
Argentina's second match in Group J is against Austria on Monday, June 22.