Ernesto Valverde hints at more signings for Barcelona after Ousmane Dembele purchase as Lionel Messi's double downs Alaves

The Catalan side made it two wins out of two in the Primera Liga as their Argentine striker netted twice after earlier missing a penalty.

Lionel Messi was Barcelona's hero in their win over Alaves as he scored twice. Vincent West / Reuters

Lionel Messi scored twice and saw a penalty saved as Barcelona maintained their perfect start to the season in the Primera Liga with a 2-0 win at Alaves on Saturday.

Without new signing Ousmane Dembele, who completed the second most expensive transfer ever by moving for €105 million (Dh459.8m) from Borussia Dortmund on Friday, or the injured Luis Suarez, Messi ensured Barca didn't lose any early ground in the title race despite a tumultuous start to the campaign off the field.

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The five-time World Player of the Year missed from the penalty spot for the 20th time in his career as Fernando Pacheco parried it away midway through the first half.

However, Messi was not to be denied as his deflected effort opened the scoring shortly after half-time before a sweetly-struck volley secured all three points.

"We're happy because we have overcome a difficult test," said Barca coach Ernesto Valverde.

"We've overcome difficult moments, we have six points and we can now move forward."

Barca's pre-season preparations were rocked by the loss of Neymar to Paris Saint-Germain for a world-record €222m.

Dembele has been bought to replace the Brazilian, but Barca's business may not be finished with a final push for Liverpool's Philippe Coutinho expected before the Spanish transfer window closes on Friday.

"We hope that by the 31st (of August) we have an even more competitive team, that is clear," added Valverde.

"We want an even better team and if there is a possibility we are open to it."

Alaves shocked Barca a year ago by winning at the Camp Nou, and the hosts were left to rue a big chance missed by Ruben Sobrino at 0-0 before succumbing to Messi's magic.

Sobrino burst past the leaden-footed Gerard Pique on the half-hour mark, but placed his shot too close to Barca keeper Marc-Andre ter Stegen as he bore down on goal.

Pique was involved at the other end as Barca were awarded a penalty moments later when he was hauled to the ground by Rodrigo Ely from a Messi free-kick.

However, Pacheco sprang to his right impressively to turn Messi's effort round the post.

Visibly annoyed at himself, Messi responded with the opening goal 11 minutes after the break as his powerful low drive struck helpless Alaves defender Alexis to fly past Pacheco.

Alexis was at fault when Barca doubled their advantage 11 minutes later as his poor clearance was headed by substitute Paco Alcacer into Messi's path to smash home on his favoured left foot.

Messi could even have had a hat-trick as he saw another effort from the edge of the box hit the bar.