The Blaugrana clinched the Copa del Rey last weekend and wrapped up La Liga on Sunday with a 4-2 victory at Deportivo La Coruna. It means the UEFA Champions League is the only major honour that's escaped them, having been knocked out by Roma in the quarter-finals.
Speaking after the win over Deportivo, in which he scored a hat-trick, the Argentinian said there was some regret at letting the European trophy slip.
"Iniesta? It's a shame about Andres," said Messi, per Football Espana. "It's a shame for us too, but he deserves to bow out like this. We have regrets about the Champions League and him not leaving with a treble, but I still think he's leaving in an impressive manner."
The 30-year-old added that he feels as though Barca have "been very superior to our rivals." "We practically didn't lose a game, one in the Copa and, unfortunately, in the Champions League, which was unexpected because of how it came about," he added.
Messi and Iniesta both spoke about their ninth league titles, per the Barcelona Twitter account:
The title triumph continued the recent stranglehold Barca have had on Spanish football in the era of Messi and Iniesta, as we can see here:
While the 3-0 loss in Rome was unexpected, overall 2017-18 has been a season to remember for the team and Messi in particular.
With Neymar departed in the summer and big-money signing Ousmane Dembele injured for the early part of the campaign, there was pressure on Messi to perform. He's relished it.
As we can see courtesy of WhoScored.com, his ability to score goals while being a source of creativity is still remarkable:
Iniesta has remained a key part of the Barcelona side this season, although there are only four more matches for him to play in the club's iconic colours.
The influence he has had on so many at Barca and across Spain has been evident since he confirmed he would be leaving. After being applauded off the field by all supporters against Sevilla last week, he received a similar ovation at the Riazor on Sunday.
Per Squawka Football, together Messi and Iniesta have helped Barcelona dominate Spanish and European football:
Messi and the rest of the team still have some big days to come before the end of the season. Next weekend they meet rivals Real Madrid in what should be a fascinating Clasico at the Camp Nou. Barcelona are also on course to become the first team to go through a La Liga season unbeaten.
The treble may have been beyond even Messi and Iniesta. But for the latter, a pair of trophies, two wins over Real Madrid and a season of domestic invincibility would be a fine way to finish.