2000–04 junior years
Messi played in Barcelona's junior Infantil B and Cadete B & A teams from 2000 to 2003 (scoring 37 goals in 30 matches in Cadete A). He was nearly released from the club in 2003 because of financial constraints, but his youth coaches convinced management to keep him (Cesc Fabregas was released during this purge). Season 2003–04 saw him on a record five different teams: He started one match in Juvenil B (one goal) and got promoted to Juvenil A (14 matches, 21 goals). Later, he debuted for the FC Barcelona C team (Tercera División) on 29 November 2003 and for FC Barcelona B (Segunda División B) on 6 March 2004. He played for both teams during the season (10 matches, five goals and five matches, zero goals, respectively). Even before these two debuts, Messi made his official debut for the first-team on 16 November 2003 aged 16 years and 145 days, in a friendly match against Porto.
Less than a year after his start, Frank Rijkaard gave him his league debut against RCD Espanyol on 16 October 2004 (at 17 years and 114 days), becoming the third-youngest player ever to play for Barcelona and youngest club player to play in La Liga, which would be broken by Bojan Krkić in September 2007. When he scored his first senior goal for the club against Albacete Balompié on 1 May 2005, Messi was 17 years, ten months and seven days old, becoming the youngest to ever score in a La Liga game for Barcelona until the record was broken by Bojan Krkić in 2007, scoring from a Messi assist. Messi said about his ex-coach Rijkaard: "I'll never forget the fact that he launched my career, that he had confidence in me while I was only sixteen or seventeen." During the season, Messi played also in Barcelona B (Segunda División B) scoring 6 goals in 17 matches.