Messi scored the opening goal of Barca's third successive Cup triumph under Luis Enrique and played a crucial role in the strikes from Neymar and Paco Alcacer which finished off the Basque minnows.
Messi became the all-time top scorer in La Liga in his first campaign under Luis Enrique, which ended with the club's second treble, and finished as the top scorer in Europe's top five leagues with 37 goals this season.
The pair's relationship appeared to be strained in the middle of that first season following a training ground bust up, which resurfaced when Messi was left out of the starting line-up in a 1-0 defeat to Real Sociedad.
But there was nothing but plaudits for the player in Luis Enrique's final news conference.
"Messi is an extra terrestrial in every sense and I'm very fortunate that I was able to enjoy the best, or one of the best, versions of him," Luis Enrique said of Messi, who collected his 30th trophy with Barcelona a month before his 30th birthday.
Luis Enrique is Barca's third most decorated coach of all time with nine trophies behind Johan Cruyff (11) and Pep Guardiola (14), who also ended his time in charge by lifting the King's Cup at the Vicente Calderon.
Luis Enrique said he had no regrets about announcing his decision to leave the club back in March.
"I'm happy about the decision I made a few months ago, it has worked out perfectly for me and the team," he added.
"This job has endless demands and after a while it takes its toll on you. But I don't feel sad, especially when I see we won nine out of 13 trophies."