Luis Suarez made it 4-0 before halftime, while Messi was replaced by Ousmane Dembele before the hour mark.
Suarez nearly capped the win with a spectacular chip from 40 yards, with the ball just sailing wide of the left-hand post, but Rakitic added gloss to the scoreline three minutes from time with a firm header from Dembele's corner.
Celta drew 2-2 in the Camp Nou in the La Liga earlier in the season and held Real Madrid to a 2-2 draw on Sunday. The Brazil midfielder will make his debut after he recovers from a right leg muscle injury.
They played very very well in their 1-1 in the first leg against Barcelona a week ago, and played just as well in a 2-2 draw against Real Madrid at the weekend.
Messi turned provider for the third, with a spectacular curled through-ball for Alba which he fired past the helpless Sergio Alvarez.
"The connection between Messi and Alba is nothing new, it has been working for years", Valverde said.
The Catalans were then held to a 1-1 draw by Juan Carlos Unzue's side as Pione Sixto cancelled out the goal scored by Barcelona B forward Jose Arnaiz in the first half.
Atletico and Sevilla is the matchup of teams better positioned in the Spanish league.
Ben Yedder scored from a rebound after a shot by Correa to give Sevilla the lead in the 32nd.
"It was a complicated match". "We are sad, but we will get through this together". Goals from Leo Baptistao and Gerard Moreno sent Espanyol through.
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