Celta Vigo faced Barcelona at Nou Camp at the Spanish League and they managed to end the game with a 2-2 draw.
Messi was on hand to double Barca's lead on the quarter-hour mark after playing Alba into space, who in turn charged down the wing and played the ball back into the path of the Argentine, who duly drilled home.
Barca boss Ernesto Valverde rested some of his best players for the first leg, including Luis Suarez and Lionel Messi, both of whom could return for the second leg. Messi will, as always, be the best player on the pitch should he feature, but Valverde could choose to give another chance to Jose Arnaiz, 22, who scored in the first leg and is the latest B-team player looking to break into the first team.
Celta have reported no injuries ahead of the match, and manager Juan Carlos Unzue will have a full squad to choose from.
"The first half was extraordinary", said Barca coach Ernesto Valverde.
The tie petered out in the second half but French global Ousmane Dembele showed why Barca shelled out £138m for him by dribbling past three defenders from the halfway line before being denied by a desperate tackle. The first Barcelona goal was a result of poor goalkeeping by Alvarez while the second was a fine team goal.
Samuel Umtiti took part in Barcelona's training session on Tuesday as the centre-back continues his recovery from a hamstring injury.
Barca eventually claimed a fifth on the night to compound the visitors' misery, Ousmane Dembele lifting a corner into the box for Ivan Rakitic to bury home with a free header into the top corner of the net from 10 yards out.
LEO MESSI put on a masterclass in front of Philippe Coutinho by netting twice as Barcelona cruised into the Cop del Rey quarter-finals.