After proving unable to keep pace with Real Madrid since the resumption, Barca ultimately surrendered their LaLiga crown in midweek after an insipid 2-1 home defeat to Osasuna.
They ended their domestic campaign in some style, though, Messi scoring twice and further goals from Ansu Fati, Luis Suarez and Nelson Semedo sealing the win.
Messi was impressed by his team-mates' response and says the commitment shown on Sunday should be the bare minimum as they look to reclaim their title next season.
He told Movistar: "As coach (Quique Setien) said the other day, we have had some very good games, some very good moments. But we have to do that more consistently now.
"Today, we saw something else. It was a difficult game to play and the team responded differently in attitude and commitment. It is a step forward for what is to come.
"We did a lot of self-criticism and realized a lot of things. We didn't have a great season.
"Today is a step forward in terms of attitude and commitment, which is what you always have to have. You have to at least match the attitude of any rival; if not more."
While their domestic duties are done for 2019-20, Barca now switch their focus to the Champions League. They host Napoli in the second leg of their last-16 tie at Camp Nou on August 8.