Although the Gunners are top as they chase a first title for 20 years, Manchester City are regarded as statistical favourites to win a fourth successive crown
Madrid have two games in hand, the first of which was supposed to take place on Sunday at Celta Vigo. However, wind damage to Celta's Balaidos stadium has left the ground unsafe to hold the game, according to the mayor of Vigo. Neither the club nor La Liga would say whether the match will go ahead however.
Barca took their chance to apply pressure at the Camp Nou, but needed some wasteful finishing by Athletic in a much tighter game than the scoreline suggests.
Luis Enrique again made a raft of changes with the second leg of Barca's Copa del Rey semi-final against Atletico Madrid looming Tuesday. Luis Suarez was left on the bench to allow Paco Alcacer a rare start and he netted his first La Liga goal since joining from Valencia for 30 million euros ($32 million) in August.
Athletic should have been in front before Alcacer's 18th minute opener as Raul Garcia's low effort was turned onto the post by Marc-Andre ter Stegen before Inaki Williams headed wide when unmarked from 12 yards out.
Alcacer has endured a torrid time since joining Barca, but settled the hosts when he turned home Neymar's cut-back inside Gorka Iraizoz's near post.
However, Barca got another break moments later when Gerard Pique was lucky to only see a yellow card for hauling down Garcia on the edge of the box.
Athletic's day was summed up with Barca's second, five minutes before half-time. After scoring in both legs of the Copa del Rey last 16 clash between the sides from free-kicks last month, Messi again outdid Iraizoz from the narrowest of angles. This time, though, the goalkeeper was more at fault than brilliance from the Argentine as Messi registered his 31st goal in 30 games this season.
Only injuries to Pique and Rafinha blighted Barca's day. Pique limped off at half-time as a precautionary measure with a groin strain, whilst the Brazilian suffered a knock in clashing with Ter Stegen.
Messi took a rare break as he was replaced with 25 minutes to go by Sergi Roberto. Yet, even that change worked in Barca's favour as Aleix Vidal was pushed into a more advanced role from right-back and rounded off the win by firing into the far corner 23 minutes from time for the Catalans' 100th goal in all competition this season.
Although the Gunners are top as they chase a first title for 20 years, Manchester City are regarded as statistical favourites to win a fourth successive crown
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