Barcelona captain Lionel Messi has branded their Supercopa de Espana defeat to Atletico Madrid as "childish".

Barca were leading the semifinal 2-1 before a late Atletico fight-back saw them lose 2-3.

"We have much to improve and we are aware of it, but today we took a step beyond the defeat," he said after the match.

"We are aware that we have not been doing things as we would have liked or the way we can.

"This year we will try to continue on the path of what we did today and not make the childish mistakes we made."

Ernesto Valverde has been criticised for Barcelona's performances and results this season, but Messi sent a message of unity to the fans.

"When there is a defeat and the targets are not achieved, it is normal for people to talk," he continued.

"We have to be more united than ever, be a strong group and move forward.

"It is a difficult situation especially because we missed out on a title that we wanted to win, [but] we have to look forward and keep growing."

The Barcelona captain was also asked whether the players have confidence in their coach.

"Yes, we are still working and trying to improve," he noted.

"Now we will have more days to prepare for the next game and think about the second round that we have ahead.

"We have much to improve. We are first [in the league], although we haven't been making good games.

"We will try to keep improving our game to keep up."