Messi's hat trick leads Barcelona to Spanish league title

It was Barcelona's seventh league title in 10 seasons and 25th overall. Madrid, last year's champion, leads with 33 La Liga trophies.

Barcelona has also thrived in the Copa del Rey, the country's second-most important club competition, winning it for the last four seasons.

Barcelona's next goal is to try to finish the league unbeaten, something which has never happened in the competition's current format.

"It's been an almost perfect season for us in the league," midfielder Sergio Busquets said.

Andres Iniesta, who last week announced he won't return for a 17th season with the club, started from the bench because of a small muscle problem. He entered the match close to the end to applause from most of the crowd at Riazor Stadium.

Iniesta and Messi each have won nine Spanish league titles.

Sunday's result relegated Clarence Seedorf's Deportivo.

The hosts paid tribute to Barcelona even before the match started with its squad lining up outside the tunnel and applauding their rivals as they entered the field. Most of the opposing fans at Riazor also applauded Barcelona's players.

Messi's fingerprints all over victory

Coutinho opened the scoring in the seventh minute with a well-placed shot into the top corner after a pass by Ousmane Dembele, and Messi added to the lead in the 38th with a strike from near the far post after a perfect cross by Luiz Suarez.

Deportivo pulled one closer with a goal by Lucas Perez in the 40th and equalized with Emre Colak's shot from inside the area in the 64th.

Messi put Barcelona ahead in the 82nd from close range after exchanging passes with Suarez inside the area, then sealed the victory in a breakaway in the 85th.

Messi has 32 league goals, leaving him with eight more than Madrid's Cristiano Ronaldo in the race for top scorer.

Disappointment for Seedorf

It has been yet another disappointing coaching stint for Seedorf, the former Dutch midfielder who earned only two victories in 13 matches since arriving to try to save Deportivo from relegation. The team has lost six times and drawn five under his command, returning to the second division for the first time since 2013-14.

"We didn't reach our goal," Seedorf said. "Now the future is open. We'll see what happens."

Seedorf was a star with the Dutch national team for more than a decade and a prominent player for Ajax, Real Madrid, Inter Milan and AC Milan. But he has achieved lackluster results in his coaching attempts, including at AC Milan in 2014.