Barcelona's quest for an unbeaten season ended in the final match of the season with their 5-4 loss at Levante.
Lionel Messi was left at home to rest.
"We've played games without Messi before and come through them," Ernesto Valverde said at his news conference. "We're all annoyed to lose. It's come in the 37th game, so it hurts to lose [the unbeaten season] now, but it could have come in the first, third or 14th game."
Barcelona last loss in La Liga on April 8, 2017.
"I feel very angry but I have to look forward because what makes me angry isn't going to give me solutions," Valverde said.
"It was a surprising game, because of the result and how it came about. [Levante] are in very good form, they are very effective, they started the game really well and caused us a lot of damage on the counter-attack."