The Catalan giants gave up in the race for La Liga's title as Atletico Madrid and Real Madrid will now fight out for the championship on the last day of the season.
Messi opened the scoring for his side with a header before Santi Mina equalised for Celta. Lenglet was shown a red card before Mina completed his brace in the 89th minute of the game.
Messi was pretty frustrated with his team's performance and beIN SPORTS has uploaded a video compilation of the player looking devastated in the aftermath of conceding the goal at Camp Nou.
Messi's deal at Barcelona will expire this summer and the Argentine has been heavily linked with a transfer away from the club, with Manchester City being his probable destination.
Meanwhile, Barcelona manager Ronald Koeman wants Messi to stay in Catalonia. Speaking after the game, Koeman said, "He has shown today it is impossible to play without him. He is still the best player in the world. He has already scored 30 goals that have earned this team a lot of points."
Koeman concluded, "It is a question for Leo to answer. As far as I'm concerned, and the team is concerned, we hope he stays because if we're not going to have Leo we will have serious doubts about who is going to score so many goals."