As it happened: Alavés v Barcelona
Messi atones for penalty miss
Barcelona secure their second win of the season with the Argentinian's two second-half goals.
Full-time! Alavés 0-2 Barcelona
Barcelona close!
Pique finds some room in the box but his shot is directed away from goal by Alexis.
Change for Barcelona
Barca make their final change as Paulinho replaces Andres Iniesta to make his debut for the club.
Double change for Alavés
Wakaso and Sobrino are replaced by Enzo Zidane and Christian Santos.
Barcelona hit the woodwork!
Messi is close to his hat-trick but his curling effort crashes off the bar.
Change for Barcelona
The away side make their second change, with Denis Suarez coming on as Deulofeu makes way
Change for Alavés
Ibai Gomez makes way for Burgui for the home side.
It's Messi again!
Paco Alcacer heads the ball to Messi after Alavés fail to clear their lines and Messi rifles the ball into the bottom right corner of the goal.
Goal Barcelona!
Chance Barcelona!
Jordi Alba has a good chance but fires over from the left-hand side of the box. He looks to have hurt himself in the process.
Change for Barcelona
After their goal, Aleix Vidal is replaced by Paco Alcacer.
Messi makes up for his penalty miss
Jordi Alba works it to Lionel Messi in the box who evades his man and his shot is deflected past Pacheco.
Goal Barcelona!
Pacheco save
A free-kick from Messi is easily saved by the Alavés goalkeeper.
Barcelona close!
Messi's curling effort from outside the box goes just over the bar.
Alavés close!
The home side have started the second half brightly, Ibai Gomez breaks down the left but his cross just evades Ruben Sobrino in the box.
Second half underway!
The home side kick off to get the second half started.
Barcelona on top
The away side have been on top here, with most of the possession, but both sides have had chances to make the breakthrough.
Half-time!
Barcelona close!
Messi plays in Deulofeu who gets behind the Alavés defence but Pacheco saves his effort.
Pique booked
Pique is booked for using his hand to try and control the ball as he headed towards goal following a good cross in from the left.
Sergi Roberto booked
Another yellow card here after Sergi Roberto goes in late on Sobrino.
Great save from Pacheco!
Messi puts the penalty low to the keeper's right but Pacheco guesses right and gets down smartly to make the save.
Penalty saved!
Yellow card Ely
The Alavés defender is booked for dragging down Pique in the box after a free-kick from Messi
Penalty Barcelona!
Wakaso cautioned
Wakaso has received a yellow card for a rough tackle on Sergi Roberto
Umtiti booked
Samuel Umtiti was shown a yellow card for his trip on Sobrino.
Barcelona break
Valverde's side counter attack from the corner and Deulofeu forces Pacheco into a save after a powerful effort from the left-hand side of the box.
Corner Alavés
The free-kick goes straight into the wall and bounces around the box before it is put out for the corner.
Umtiti booked
Samuel Umtiti is shown a yellow card for his trip on Sobrino.
Free kick Alavés
It's in a dangerous position here, after Umtiti tripped Sobrino on the edge of the box.
Barcelona close!
Lionel Messi dances his way into the box and fires a shot in from a tight angle near the by-line but Alavés manage to clear.
Pacheco saves again
It's another comfortable stop for the Alavés keeper, who saves a tame effort from Lionel Messi
Roberto at right-back
It looks as if Aleix Vidal if operating on the right wing, with Sergio Roberto just behind him at right-back and Iniesta playing just behind Messi.
One-way traffic
Barcelona have enjoyed 71% of possession so far and are pretty much camped in the Alavés half. They are yet to make this dominance show though.
Barcelona very fluid
It is unclear what system the Catalan side are playing as many of their players are roaming around freely.
Alavés close!
Sobrino prods just wide from a shot/cross in from the left from Pedraza. The striker should have done better but luckily for him he was flagged offside anyway.
Pacheco save
Rakitic gets in behind the Alavés defence but directs his low cross straight into the hands of Pacheco
Barcelona on top
In the first five minutes Barcelona have seen most of the ball but are yet to fashion out a real chance.
Pacheco save
Gerard Deulofeu tries an effort from the edge of the box but it is comfortably saved by Pacheco
Alavés close!
Ter Stegen tips a free-kick from Alavés over the bar.
And we're off!
Barcelona kick-off to get this match started.
How will Barcelona set up?
With only two forwards on the pitch, could we see the versatile Sergi Roberto or the experienced Andres Iniesta play on the right wing for Ernesto Valverde's side?
Dembélé not ready yet
Barcelona's new signing Ousmane Dembélé is not yet ready to feature for his new club but the Catalan side will hope to make it two wins out of two in La Liga and Alavés will look to pick up their first points of the season in the first meeting between these two teams since last year's Copa del Rey final.
The lineups are out!
Alavés starting XI: Pacheco; Pedraza, Aleix, Ely, Vigaray; Gómez, Garcia, Romero, Pina, Wakaso; Sobrino
Subs: Sivera, Duarte, Maripan, Santos, Burgui, Torres, Zidane
Barcelona starting XI: Ter Stegen; Alba, Pique, Umtiti, Vidal; Roberto, Rakitic, Busquets; Iniesta, Messi, Deulofeu
Subs: Cillessen, Mascherano, Semedo, Digne, D.Suarez, Paulinho, Alcacer
Live updates of the La Liga match between Alavés and Barcelona at the Mendizorrotza Stadium