The Argentina superstar had been unusually subdued for much of the match, appearing a little off the pace, but he produced a ferocious 25-yard effort in the second half to ensure he finishes the sixth successive calendar year with at least half a century of goals.
Alaves kept Barca at bay for only 14 minutes, as Antoine Griezmann scored his fourth goal in seven matches across all competitions, and Arturo Vidal doubled their lead with a fierce strike just before half-time.
The visitors did hit back through Pere Pons early in the second half, offering them encouragement, but Messi effectively ended their hopes with his wonderful strike and Luis Suarez – who had set up the first three goals – deservedly got in on the act late on from a controversial penalty.
The warning signs were there early on for Alaves, as Messi had a goal disallowed in the 10th minute as a VAR review identified him to have strayed marginally offside.
But with their next move, Barca opened the scoring – Griezmann placing a right-footed effort into the bottom-right corner from the edge of the box following Suarez’s lay off.
Vidal was similarly decisive late in the half, receiving Suarez’s pass and blasting an emphatic strike in across goal.
Alaves began the second period brightly and got themselves a lifeline through Pons’ powerful header, leaving Marc-Andre ter Stegen no chance when arriving late to meet Ruben Duarte’s cross.
But Messi turned on the style 21 minutes from time when lashing in from almost 30 yards despite being seemingly surrounded.
And the excellent Suarez rounded off the scoring soon after, converting from 12 yards after a VAR review deemed Martin Aguirregabiria to have handled the Uruguayan’s previous header.
What does it mean? Barca set to start 2020 top
Although the scoreline arguably flattered Barca, there was rarely any doubt about who was going to win and the victory means they should begin the New Year top of the league.
Only a remarkable result in Real Madrid‘s match against Athletic Bilbao will prevent that.
Suarez knits it all together
Several Barca players have come in for significant criticism this season, with Suarez among them. But on Saturday he was excellent, playing a hand in all four goals. His awareness when setting up the first three was particularly impressive.
Ely fails to halt Suarez
The man tasked with keeping Suarez under control was Rodrigo Ely. The Brazilian failed. He barely got near the striker all match and had a miserable outing.
Key Opta Facts
– Suarez is the first player to provide three assists in a single LaLiga game this season.
– Barcelona have scored 6136 goals in LaLiga history, only one fewer than Real Madrid (6137 with a game fewer)
– Griezmann has scored three goals in his last four LaLiga games, one fewer than he had in his previous 13 matches for Barca in the competition.
– Vidal has scored five goals in 14 appearances in LaLiga this season, two more than he had last season (three goals in 33 matches).
This is the fourth game in which Barcelona trio Messi, Suarez and Griezmann have scored together in all competitions and the third at Camp Nou.