Trincao opened the scoring after half an hour and Messi added Barca's second at Camp Nou in first-half stoppage time from 30 yards minutes after having a goal ruled out for offside. Luis Rioja capitalised on a defensive mistake in the 57th minute to briefly give Alaves hope of a comeback before Ronald Koeman's side pulled away in the final stretch of the game. Trincao scored his second of the night in the 74th minute and Messi, with another stunning long-ranger, followed suit a minute later. Defender Junior Firpo completed the rout late on.
This was the perfect way to warm up for Tuesday's Champions League last-16 tie against PSG at Camp Nou. Koeman was able to rest several important players at various stages of the game while still earning a handsome win to remain within eight points of leaders Atletico Madrid -- albeit having played a game more.
Five La Masia players started the game, including 18-year-old midfielder Ilaix Moriba, who was making his first-ever appearance in La Liga. He set up the first goal, although he gave the ball away in the second half to inadvertently set up Alaves' goal.
As for Messi, he's in great form, taking his scoring streak in La Liga to five games for the first time since April 2019. And Trincao found that goals are very much like London buses; he waited for 27 games before breaking his duck against Real Betis last weekend, and he scored two more here and could have scored a hat trick.
Barca once again gave up a lot of chances with sloppy passing in the middle and passive defending. Alaves took only one of them, but if Lucas Perez had his shooting boots on, they might have scored more.
Manager rating out of 10
7 -- Koeman kept players fresh for PSG, and those he brought in, such as Trincao, Riqui Puig and Junior, delivered on the pitch to make it the perfect night for the Dutch coach.
Player ratings (1-10; 10 = best. Players introduced after 70 minutes get no rating)
DF Oscar Mingueza, 6 -- Was part of a three-man defence without the ball and was a right-wing-back with the ball. Better at defending but is improving in attack, with his cross leading to the opening goal.
DF Frenkie de Jong, 6 -- A rest for the Dutch midfielder these days seems to mean playing at centre-back. Did well without having to exert himself.
DF Clement Lenglet, 6 -- Did OK but still looks short of confidence, which is worrying going into the PSG game.
DF Junior Firpo, 7 -- Has done well when given a chance in recent weeks and got forward to take his goal well.
MF Sergio Busquets, 7 -- Played only 45 minutes with PSG in mind but made two of the game's best passes: one over the top for Antoine Griezmann before a disallowed Messi goal and another into Messi's feet for Barca's second.
MF Ilaix Moriba, 6 -- Good composure to set up the goal but erred with a pass to give one away, too. Overall, a memorable night as he made his La Liga debut.
MF Riqui Puig, 7 -- A rare 90 minutes for the young midfielder who got better as the game went on. Linked well with his teammates and showed variety with his passing.
FW Francisco Trincao, 8 -- Took both his goals well and could have scored a hat trick. Denied by Fernando Pacheco when he should have passed to Ilaix and had a late effort ruled out for offside.
FW Lionel Messi, 9 -- Scored two goals of the highest quality and had a third ruled out for offside. Now has 15 in La Liga, just one fewer than top scorer Luis Suarez.
FW Antoine Griezmann, 6 -- Improved in the second half with some nice touches and was involved in a couple of the goals. Missed his best chances, though, including a second-half volley from close range after a fine Messi pass.
DF Samuel Umtiti, 6 -- Didn't do a lot wrong but was far too passive for Rioja's goal and showed him into far too much space.
MF Pedri, 8 -- It's not a coincidence that he came on at 2-1 and the game finished 5-1. A brilliant pass to Messi led to Trincao's second goal.
MF Miralem Pjanic, N/R -- Came on to give De Jong a breather.
DF Sergino Dest, N/R -- Returned from a thigh problem late on to get some important minutes pre-PSG.
FW Ousmane Dembele, N/R -- Given the final few minutes in place of Griezmann.