Lionel Messi was left to rue a series of "childish mistakes" in Jeddah as his Barcelona side crashed out of the Supercopa at the hands of Atletico Madrid .
In the first-ever playing of the new-look competition in Saudi Arabia, Barca went behind to a goal from Koke seconds after the game restarted after half time.
The Catalans rallied, with Messi and Antoine Griezmann - scoring his first goal against his former employers - turning the tables and Barca also seeing two goals disallowed via VAR.
Alvaro Morata then restored parity to 2-2 from the penalty spot, and Atleti were unlucky not to receive another spot-kick in a frantic finale before Angel Correa scored the decisive goal four minutes from the end.
Atletico go on to face Madrid rivals Real in the final on Sunday while Barca prepare for an early flight home, to the evident displeasure of their captain.
"It is a shame, we played a great game, after so long we felt good again, we were in control, dominated and attacked all the time," Messi told reporters in Jeddah.
"We let it slip through certain mistakes when [Atletico] were already almost dead, in less than 10 minutes they turned round a game that we should have seen out.
"It hurts because it is a title and we wanted to be in the final and win it, we showed a different side to what we have been showing recently against Espanyol and at the end of last year, we played a good game but sadly we couldn't get the victory.
"We have taken a step forward today despite the defeat but we are aware that we have not been doing things the way we want, we do not want to make these childish mistakes again."
Defeat has once more placed Ernesto Valverde under the spotlight , with the coach the target of criticisms from Barca fans for his side's mixed performances.
Messi admitted that the pressure was on, but called on the Catalans to show a united front as they prepare for the final months of the 2019-20 season.
"We will keep working and trying to improve, now we will have more days to prepare for the next game, we have to improve a lot and despite the fact that we have not been playing well we will try to get our play back," he added.
"It is normal when there are defeats and we don't achieve our goals, the fans see that their team isn't playing as they would like, as we would like, it is normal for them to speak out but we have to be more together than ever, it is a difficult situation because we let slip a title that we wanted to win but we have to look forward."