WATCH: Barcelona mark 15-year anniversary of Messi's first match
Then just 16, Messi was introduced off the bench against Jose Mourinho's Porto in a friendly on November 16, 2003.
The match was organised to celebrate the opening of Estadio do Dragao ahead of Euro 2004 but has been remembered for the emergence of a budding superstar.
In the video, posted to social media on Friday, a young Messi admits to costing himself the chance of a brace through a combination of unselfishness and an uncharacteristically nervous first touch.
His team-mates in the 2-0 defeat included midfield great Xavi, long-serving defender Rafael Marquez and future Barca boss Luis Enrique.
Then-coach Frank Rijkaard made the teenager wait for his first competitive appearance, which came in October 2004 in a LaLiga win over rivals Espanyol.
Leo #Messi 15 years since the made his debut! pic.twitter.com/6jAoHMLeK0
— FC Barcelona (@FCBarcelona) November 16, 2018