Neymar opened the scoring with a simple finish from Messi's through ball before the Argentine star missed from the spot for the 12th time in his career after Loukas Vyntra had seen red for tripping him inside the area on Sunday.
     
However, it mattered little as Ivan Rakitic's fierce strike made it 2-0 before half-time and goals from Sandro Ramirez, Pedro Rodriguez and Messi rounded off the scoring after the break to make it four wins in four La Liga games without conceding a goal for Barca.
     
Barca now lead second-placed Sevilla by two points with champions Atletico Madrid a further two points adrift and Real Madrid six back in seventh.
     
"Once we have played a more significant amount of games we will look at the table and analyse our situation," said Barca boss Luis Enrique.
     
"But the season has just started and there will be a lot of changes in the table to come,” he added.
     
Enrique recalled many of his rested stars for Wednesday's 1-0 win over APOEL Nicosia in the Champions League as he made eight changes in all with only Messi, Neymar and Dani Alves retaining their places in the side.
     
However, only a last-ditch challenge from Rakitic prevented Victor Casadesus turning home Jose Luis Morales's cross at the far post to give the side rooted to the foot of the table a shock lead after 15 minutes.
     
Barca then slowly began to take charge and after Jordi Alba fired wastefully off target, Neymar was denied at the end of a flowing move by a brave block from Jesus Fernandez.
     
The Brazilian got the better of Fernandez just after the half hour mark, though, as he latched onto Messi's ball over the top and rounded the 'keeper before slotting home his third goal of the season.
     
Barca looked to have the game sealed when Messi was then tripped inside the area and Greek defender Vyntra harshly sent-off for denying a clear goal scoring opportunity.
     
Messi picked himself up to take the resulting spot-kick, but blasted his effort high and wide of the target.
     
The Argentine's blushes were spared as Rakitic rifled in his first goal for the club from outside the box shortly afterwards to ensure the visitors led 2-0 at the break.
     
There was a brief scare for Barca when Neymar went down with an ankle injury at the start of the second period, but his protestations at being replaced by Sandro suggest the injury shouldn't keep him out of Wednesday's trip to Malaga.
     
Sandro then got himself on the score sheet as he became the latest recipient of a Messi assist with a low right-footed finish.
     
Pedro registered his first goal of the season to make it 4-0 26 minutes from time as he rolled the ball into an empty net after a lovely one-two between Alba and Sandro.      

And Messi finally got his reward for another fine performance when he pounced on a poor clearance from Fernandez and lobbed the ball over the 'keeper for his third goal of the campaign.
     
Earlier, Sevilla had briefly moved top with a 3-1 win at Cordoba thanks to two goals from Colombian international Carlos Bacca.
     
Villarreal moved into the top six as they came from 2-0 down to beat Rayo Vallecano 4-2 at home, but Real Sociedad failed to move into the top half of the table as they were shocked 2-1 at home by Almeria.

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