Messi's goal was his 30th in La Liga this campaign, meaning he's hit 30 or more goals in nine different seasons. There was also more playing time for young midfielder Ilaix Moriba, who did OK filling in for the suspended Frenkie de Jong.
You can copy and paste the summary from the majority of Barca's last five games here. As was the case against Granada and Levante, Barca contrived to throw away a lead through a combination of failing to take their chances and poor defending. Before that Granada game at the end of April, a win would have taken them top, but a run of one win in five games sees them end the season third regardless of what happens next weekend.
The toughest thing for Ronald Koeman's side to take is that they fought back from 13 points behind Atletico to take their fate back into their own hands. To throw it away as they have done has been unacceptable.
Manager rating out of 10
4 -- Koeman may have managed his last game as Barca coach at Camp Nou. A Copa del Rey win may not be enough to save him from the sack with such glaring errors in his tactical setup once again on show against Celta.
Player ratings (1-10; 10 = best. Players introduced after 70 minutes get no rating)
GK Marc-Andre ter Stegen, 5 -- Bizarrely didn't even move for the first Mina goal, perhaps because he was unsighted, but it did not look good.
DF Ronald Araujo, 6 -- His pace and strength were handy in the second half when Barca switched to a back four and were then later reduced to 10 men, but he was slow to react for Mina's winner.
DF Gerard Pique, 5 -- Stood miles off Mina to allow him a free shot for the first goal. Has shown signs of his age in this run-in.
DF Clement Lenglet, 4 -- The Frenchman's season is over. His second red card of the campaign, completely deserved for two yellow card offences, means he will miss the final game at Eibar next week.
MF Ousmane Dembele, 6 -- Caused problems with his pace and directness on the right, but wasn't clear-minded enough in the final third.
MF Ilaix Moriba, 6 -- Not his best performance, but he does at least look accomplished at this level. Used his body well to protect the ball.
MF Sergio Busquets, 6 -- Produced a great pass to set up Messi's goal. Has benefitted from the switch to 3-5-2, though long-term questions will persist about his ability in a 4-3-3.
MF Pedri, 6 -- A tired end to the season saw him removed at half-time. Worked hard until then, winning balls back to set up counters on several occasions.
MF Jordi Alba, 6 -- Got into good positions on the left but couldn't create as much as he often does.
FW Lionel Messi, 7 -- Took his goal well with his head and almost stole a late equaliser, firing just wide after a good run.
FW Antoine Griezmann, 5 -- The French forward was unable to make any sort of difference on the outcome of the game, drifting in and out of different positions.
MF Riqui Puig, 6 -- Added energy, but his performance was lacking quality, although that's to be expected given his lack of minutes this season.
DF Sergino Dest, 5 -- Replaced Pique as Koeman changed the shape.
MF Francisco Trincao, 6 -- Had a couple of nice runs, but always in areas of the pitch where he couldn't do much damage.
FW Martin Braithwaite, 5 -- Missed a great chance to make it 2-1 before Celta's winner.
MF Miralem Pjanic, NR -- Brought on for Ilaix after Lenglet's late red card.