Atletico Madrid pipped city rivals Real Madrid to the title after Luis Suarez fired them to a 2-1 comeback win at Real Valladolid.
Atletico Madrid took a giant step towards the La Liga title in dramatic circumstances by fighting their way back to beat Osasuna 2-1 at home thanks to a late strike from Luis Suarez.
He will almost certainly also miss his club's La Liga match against his former club Barcelona on November 21.
The Uruguayan striker also revealed he was not allowed to take part in training matches.
Messi has launched his latest attack on Barcelona's hierarchy by criticising the way the club treated strike partner Suarez, who left for La Liga rivals Atletico Madrid this week.
Barca's statement said Atletico will pay the Catalans six million euros in bonus payments to sign the 33-year-old.
The Catalans' third top scorer of all time was told he was not wanted by new Barcelona coach Ronald Koeman and has been looking for a new club.
Under the terms of the contract which expires in 2021, the only way Messi can leave without the club's consent is if a rival side pays his release clause of 700 million euros (629.7 million pounds).
Catalan radio station Rac1 reported that the striker had been told by new Barca coach Ronald Koeman that he was not in his plans for next season.
Barca, chasing a third consecutive Spanish title, are on 76 points after 35 games while Real Madrid are top with 77 and can restore their four-point advantage when they host Alaves on Friday.