By Gabriel Tan
Barca went behind in the 17th minute after Joseba Llorente found the back of the net with a well-taken volley, but Messi pulled them level in the 75th minute, before grabbing a winner ten minutes later.
The result also allowed Tito Vilanova's men to establish a five-point lead over Real Madrid after the reigning champions fell to a shock 2-1 defeat at the hands of Getafe, despite taking the lead.
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Valencia made it two draws from two after throwing away a two-goal lead to draw with Deportivo La Coruna 3-3, while Atletico Madrid cruised to a 4-0 defeat of Athletic Bilbao, the side they beat in last season's Europa League final.
Elsewhere, Rayo Vallecano recorded a 2-1 win at Real Betis, Granada and Sevilla played out a 1-1 draw in the first Andalusian derby of the campaign, while Real Zaragoza toiled to a 2-1 triumph at Espanyol.
Here, ESPNSTAR.com takes a look at the best eleven players from La Liga this week.
GK: Gustavo Munua (Levante)
Levante may have fallen to a 2-0 defeat at the hands of newly-promoted Real Valladolid on Monday evening, but the scoreline would have been much worse had it not been for the heroics of Munua.
With Valladolid enjoying 77% of possession, they were always going to have their fair share of chances and the Levante custodian reacted sharply to keep out a strong header from Javi Guerra early on, before smartly tipping a fierce drive from Patrick Ebert over the bar just before the break.
And with the hosts already two goals to the good, Munua kept the scoreline respectable late on as he made himself big to keep out a close-range effort from Juan Neira, and was the only Levante player unlucky to be on the losing side on the night.
RB: Juan Valera (Getafe)
Valera remains one of the most-underrated players in the league but the versatile defender showed just what he's capable of on Sunday as he helped Getafe to a shock win over Real.
Despite coming up against one of the world's top-two players in Cristiano Ronaldo, the former Atletico man kept his opponent quiet all evening long and even popped forward to good effect, pulling his side level in the 52nd minute when he glanced home an Abdelaziz Barrada freekick.
CB: Javi Fuego (Rayo Vallecano)
Rayo maintained their 100% start to the season at the weekend by beating Betis and plenty of credit has to go to Fuego, who put in a captain's display by ushering his defence with authority all game long.
The 28-year-old completely nullified the threat of Jorge Molina, apart from the one moment when the Betis striker was allowed to sneak in and score, and Rayo's supremacy at the back set the tone for their victory.
CB: Pedro Bigas (Real Mallorca)
While he is naturally a left-sided player, the 21-year-old was named in the heart of defence by Mallorca coach Joaquin Caparros for Saturday's match against Malaga, and repaid his boss' faith with a commanding display.
Bigas' keen reading of the game was clear for all to see as he made a number of vital interceptions, ensuring the Malaga attacking trio had little to work with for the full 90 minutes.
LB: Jordi Alba (Barcelona)
The new campaign may only be two weeks old but Alba is already proving to be a shrewd buy by Barca coach Tito Vilanova given the way he has seamlessly replaced Eric Abidal and fitted into the starting XI.
On Sunday, the Spain international also showed his full array of attacking qualities - on area that Abidal lacked in - when he ventured forward and picked out the perfect pass for Messi to stroke home the winner for the Catalan outfit.
DM: Ignacio Camacho (Malaga)
Camacho showed on Saturday why he was once regarded as the next big thing in Spanish football with an accomplished display in the heart of the Malaga midfield.
Often compared to Xabi Alonso throughout his teenage years, the ex-Atletico youngster broke down opposition attacks with his tenacious chasing but was then equally capable of initiating attacks with his short but incisive passes.
CM: Mikel Rico (Granada)
The 27-year-old was at his all-action best for Granada at the weekend as he left the Sevilla midfielders chasing his shadow in the first Andalusian derby of the season.
Renowned for his knack on delivering the goods on big occasions, Rico reacted the fastest to hand his side the lead in the 34th minute when he tapped home the rebound after Guilherme Siqueira's penalty had been saved by Andres Palop, although it wasn't enough for all three points as the visitors went on to grab an equaliser ten minutes after.
CM: Abel Aguilar (Deportivo La Coruna)
Deportivo had looked dead and buried at halftime at the Mestalla on Sunday, trailing Valencia 3-1 although Aguilar's 38th-minute strike ensured a comeback was still possible if not probable.
And in the second half, that was exactly was Deportivo did, with the Colombia international leading the way by pulling another back before the hour mark when he converted a cut-back from Aythami, setting the stage for Pizzi to rescue a point from the spot in the 76th minute.
RF: Leo Baptistao (Rayo Vallecano)
Spain's top flight is known for producing its fair share of promising youngsters and last week, we saw the birth of a potential star when 16-year-old Fabrice Olinga became the youngest player ever to score in La Liga.
This week, we were introduced to Leo, who displayed his precocious talent in Rayo's triumph over Betis. Within two minutes, the 20-year-old laid on the perfect cross for Piti to tap home, before he went on to grab his side a deserved winner in the 60th minute when he rifled a shot past Fabricio.
LF: Lionel Messi (Barcelona)
With 75 minutes gone and a goal down, Barca were looking headed for a shock defeat at the hands of Osasuna thanks to Llorente's 17th-minute opener.
As usual, step forward Messi, who equalised for his side when he popped up in the right place at the right time to stab home Alexis Sanchez's cross, before stealing all three points ten minutes later when he clinically rolled a shot into the far corner after being picked out by Alba.
CF: Radamel Falcao (Atletico Madrid)
If he wasn't playing in the same league as Messi and Ronaldo, one wonders how much attention Falcao would actually get.
The prolific Colombian netted 37 goals last term in his first season at the Vicente Calderon, and he opened his account for the new campaign with three against Bilbao on Monday. His first came via a brilliant individual effort in the 19th minute when he received a throw-in and turned Carlos Gurpegui fluidly, before dinking a shot over the onrushing Gorka Iraizoz and into the back of the net.
Just before halftime, he made it two when he slotted home a Diego Godin cross at the far post, before completing his hat-trick from the spot three minutes before the hour mark, after Gurpegui was harshly penalised for handball inside the area.