Two decades on, the Argentine has evolved from a promising, tricky winger to the best player in history, racking up a list of records, accolades and awards longer than any other the sport has ever seen.
Messi has achieved notable feats with Paris Saint-Germain, Inter Miami and especially Argentina, whom he has led to three successive major trophies - including long-awaited World Cup glory in 2022 - in one of the most dominant eras of international football ever.
However, it is with Barcelona that he remains most intrinsically associated, having been on the club's books for 21 years - including 17 in the first team - before his tearful, heart-wrenching and reluctant departure in 2021.
Messi made 778 appearances for the club, directly contributing to a frankly incomprehensible 977 goals in that time, scoring 672 himself and setting up a further 305.
All of those tallies are unsurprisingly club records, and helped him inspire Barca to 10 La Liga titles, four Champions Leagues and seven Copas del Rey, amongst other trophies, during a silverware-laden stay at Camp Nou.
A 6/10 performance for Messi would be regarded as a man-of-the-match display for most players, but often the Argentine has reached levels of performance which few - if any - in the history of the sport can match.
With that in mind, and to mark the anniversary of his debut, Sports Mole has taken on the thoroughly enjoyable task of picking out Messi's 20 greatest ever Barcelona performances - try as we might, we could not cut the list down any more, and we are still omitting some displays which would be career-defining matches for most players.
Sit back and enjoy the very best of the best!
20. Barcelona 2-0 Manchester United (May 27, 2009)
It is a mark of the ludicrous standard in this list that a superb performance in a Champions League final only makes it to number 20.
The buildup to the 2009 Champions League final was all about Messi vs. Cristiano Ronaldo - a rivalry which was still in its early stages but which had already generated significant hype even before the latter's move to Real Madrid.
Ronaldo already had one Ballon d'Or under his belt heading into the Rome showdown but Messi was on course to usurp his great rival as the world's best player, and his performance at the Stadio Olimpico went a long way towards sealing his first of eight.
Despite pre-match talk of Ronaldo's aerial ability being a major advantage he had over Messi, it was the Argentine who used his head to greater effect as Pep Guardiola's side clinched Champions League glory.
A one-booted Messi produced a gravity-defying leap to send a looping header over Edwin van der Sar and into the back of the net, sealing a third Champions League title for his club and capping another fine individual performance on the biggest stage.
19. Barcelona 4-0 Bayern Munich (April 8, 2009)
Barcelona have suffered more recent Champions League humiliation at the hands of Bayern Munich, but in 2009 it was their turn to inflict punishment on the German giants as they effectively booked their place in the semi-finals with a game to spare.
Messi opened the scoring after only nine minutes by rolling the ball into the bottom corner, and added an assist just three minutes later with a reverse pass through for Samuel Eto'o to finish.
The Argentine netted his second of the game and Barcelona's third in the 38th minute, diving in to bravely prod home from close range.
Messi was also heavily involved in the buildup for the fourth goal as Barcelona put the game beyond the Bavarians before half time of the first leg, remaining on course for the Champions League glory they achieved that year.
18. Barcelona 5-0 Eibar (February 22, 2020)
The most recent entry on this list, Messi's seventh four-goal haul of his career came in a 5-0 rout of Eibar in February of last year.
Messi's first was the pick of the bunch as he skipped past three defenders before applying a brilliant finish, but his second and fourth goals were also fine solo efforts in their own right.
The Argentine had the run of the place as he burst past two more defenders and slotted home for his second, clipped a loose ball home for his hat-trick having tried to set up Antoine Griezmann and then toyed with the Eibar goalkeeper for his fourth goal.
By this stage of his career the supporting cast that had played such a big role in many of the other inclusions on this list had largely broken up, but this game was a firm reminder - if one was needed - that Messi could still produce other-worldly performances regardless of who is around him.
17. Barcelona 5-0 Atletico Madrid (September 24, 2011)
Messi has a million ways to make goalkeepers look silly, and one of his favourites is to beat them at their near post - just as he did to Thibaut Courtois for his brilliant opening goal in this rout of Atletico Madrid early in the 2011-12 season.
That goal made it 3-0 after just 26 minutes, with Messi having already forced an own goal to chalk up an assist, and he went on to add two more goals in the second half for yet another hat-trick.
The number 10's second goal was arguably even better as he pounced on a loose ball before coasting past a couple of defenders and firing home through the legs of a third, and there was another nutmeg to complete the hat-trick as he beat Courtois from a tight angle again.
The performance came just a week after scoring a hat-trick and claiming two assists against Osasuna, offering early glimpses of what was to come in a season which saw him score an unprecedented 50 goals in the league alone.
16. Barcelona 5-2 Getafe (April 18, 2007)
Picking out Lionel Messi's greatest ever goal is a whole different rabbit hole of footballing splendour to go down but, despite there being so many to choose from, you will be hard-pressed to find one better than his solo effort against Getafe in 2007.
Messi had already begun to build his reputation as Diego Maradona's long-awaited worthy heir by this stage, and the comparisons between the diminutive duo only grew when Messi produced a piece of genius eerily reminiscent of Maradona's 'Goal of the Century' against England at the 1986 World Cup.
Indeed, the strike was voted as Barcelona's greatest ever goal - just one of the countless indelible marks Messi has made on the club.
While such a moment unsurprisingly stole the headlines as the standout feature of the match, Messi also set up the opening goal for Xavi and lashed home the third - all within the first half.
The Argentine's magic appeared to be enough to send Barca into the Copa del Rey final, but without Messi in the squad they contrived to lose the second leg of the semi-final 4-0 as Getafe pulled off a stunning comeback.
15. Barcelona 4-0 Manchester City (October 19, 2016)
Having wreaked such havoc as a Barcelona player under Guardiola, Messi came back to haunt his former manager in the way only he can during this Champions League group game in 2016.
The striker took advantage of some statuesque Man City defending to open the scoring after 17 minutes, but it was in the final half an hour of the game - after Man City had been reduced to 10 men - where he really took matters into his own hands.
An eight-minute brace saw Messi complete his hat-trick, before winning a penalty which Neymar subsequently saw saved by replacement keeper Willy Caballero.
Barca would not be denied their fourth, though, with Messi teeing up Neymar again just two minutes later and the Brazilian this time making no mistake as their reunion with their most successful ever boss ended in a 4-0 triumph.
14. Real Madrid 2-6 Barcelona (May 2, 2009)
Pointing out that playing a starring role in a six-goal showing away to Real Madrid was one of the standout performances of Messi's career may be stating the obvious, but the importance of this particular game goes even further than the fact that Barcelona recorded their biggest ever win at the Bernabeu.
Deployed as a 'false nine' for the first time by Guardiola, Messi assisted Barcelona's first goal for Thierry Henry to level the scores after 18 minutes and then went on to add two more of his own.
The first was a poked finish 10 minutes before half time, while his second saw him toy with Casillas before beating him at the near post to make it 5-2.
Messi will feel that he could and should have had more too, missing three very presentable chances and coming close with an audacious lob in addition to his two goals and one assist.
Even so, he had once again made the Bernabeu his playground as Barcelona enjoyed arguably the standout moment of an incredible season in which they became the first Spanish club to win the treble.
13. Barcelona 4-0 Espanyol (May 5, 2012)
Always the man for a big occasion, Messi ensured that Guardiola's final home game in charge of the club - a derby against local rivals Espanyol, no less - was marked in suitable style.
It came at the end of a season in which Messi in particular reached new heights, and it was his opening goal of the contest - a pinpoint 30-yard free kick - which was the pick of his four on the night.
The Argentine rippled the side-netting with another before adding a hat-trick in the final 30 minutes - two from the penalty spot, including one he won himself, and a brilliant effort to secure the matchball sandwiched between those spot kicks.
It was one of eight four-goal hauls in Messi's career and his third of the Guardiola era, bidding farewell to the man who got the most out of him in fine fashion.
12. Levante 0-5 Barcelona (December 16, 2018)
As far as decisive influence on a single game is concerned, this might just be top of the pile throughout all 768 of Messi's Barcelona appearances.
The Argentine scored three and created two more to single-handedly tear Levante apart, directly contributing to all five goals in a 5-0 hammering and setting the tone with his impossible opening assist for Luis Suarez 10 minutes before half time.