Few could have imagined that his appearance as an 82nd-minute substitute for match-winner Deco in a 1-0 victory at Espanyol would be the first step towards a career many consider the greatest of all time.
Since that day, Messi has won 10 LaLiga titles, the Copa del Rey six times and the Champions League on four occasions, as well as becoming an unprecedented six-time winner of the prestigious Ballon d'Or award.
To mark the anniversary of Messi's LaLiga debut, we have analyzed the Opta numbers behind a genius.
A CLASS OF HIS OWN
During his 16 years in Barca's first team, Messi has become the club's all-time leading goalscorer with a whopping 635 in total.
Of that number, 445 have come in LaLiga, which means he also has the most in the history of Spain's top flight. Messi has 115 in the Champions League, 53 in the Copa del Rey, 14 in the Supercopa, three in the UEFA Super Cup and five in the Club World Cup.
His first Barcelona goal came against Albacete on May 1, 2005, with fellow superstar Ronaldinho setting him up.
The Argentina great enjoyed his most prolific campaign in the 2011-12 campaign, when he scored 73 goals across all competitions for Barcelona. There were an eye-watering 79 across the calendar year in 2012.
As well as his extraordinary goals return, Messi also has 254 assists for Barca – 183 of which have come in LaLiga and 33 in the Champions League.
LOVE FOR PEP, TITO AND SEVILLA
It should come as little surprise that some of Messi's best returns in a Barca jersey have come playing in the golden era of Pep Guardiola.
In total, Messi had 211 goals and 79 assists in 219 games played under the now-Manchester City manager – an average of 0.96 goals per game.
He also excelled under Luis Enrique, winning the second of his career trebles. There were 153 goals, 66 assists and a goals-per-game ratio of 0.97 in that period.
But it was actually Tito Vilanova for whom Messi returned the best goals per game, a mind-boggling 1.2, having scored 60 in 50 appearances.
As many as 79 different teams have conceded to Messi but none have picked the ball out of the net on more occasions against the Argentina great than Sevilla, who have done so 37 times.
LUCKLESS ALVES, SUAREZ AFFINITY AND GLORY AT THE BERNABEU
Not many goalkeepers can say they have got the better of Messi and Diego Alves in particular has not enjoyed encounters against the mercurial forward.
Messi scored past the former Valencia stopper on 21 occasions, with Gorka Iraizoz next on the list - having shipped 18 to the Argentina captain. Iker Casillas and Andres Fernandez have been beaten 17 times.
At Barca, Messi has played alongside some of the best players of his, or indeed any, generation.
But no player has assisted Messi more than Luis Suarez, who has now left Barca for Atleti, with the Uruguay star setting up his former team-mate on 47 occasions.
Camp Nou is of course the venue where Messi has scored the majority of his goals but the Santiago Bernabeu is next highest, with the 33-year-old having celebrated 15 strikes there.
The Riazor is where Messi has his best goals-per-game ratio at 1.63, scoring 13 times in eight games played at the home of Deportivo La Coruna.
THE OPTA FACTS
- Messi is the all-time LaLiga scorer with 445 goals, becoming second-highest scorer in the top-five European leagues after Cristiano Ronaldo (450).
- Since 2008-09 to 2019-20, Messi has scored 30-plus goals in each of his 12 campaigns.
- He is the only player to score 10-plus goals in LaLiga in 14 consecutive seasons, netting 50 goals in 2011-12, the most by a player in a single season in the competition's history.
- Messi scored in 21 consecutive LaLiga games between November 2012 and May 2013, the best run of any player in Spain's top flight.
- As well as being the all-time top-scorer in El Clasico with 26 goals, Messi is the leading scorer in the Catalonian derby against Espanyol (25 goals).
- He is one of the two players in Champions League history to score 100+ goals (115), alongside Ronaldo (130).
- Messi was the first player to score five goals in a single Champions League match, versus Bayer Leverkusen in March 2012 at Camp Nou.
- He is one of the six players to reach 50-plus goals in the Copa del Rey (53 goals) and one of the two to have scored in five different Copa del Rey finals after Telmo Zarra.