The result also ended Gerardo Martino's reign as manager and Mascherano made sure to apologise for the season, but also hinted at big changes throughout the club to mark "the end of a cycle".
"It's the end of a cycle. We apologise to everyone. The manager, the fans, everyone," Mascherano told reporters. "Losing in front of our fans hurts a lot. We've been through the ringer this season.
"We could've won and left everything behind. Now there will be decisions, and changes, of course. This season wasn't the best, far from it.
"We'll have to wait for next season to see what decisions the club makes."
Barcelona finished the campaign in second place in La Liga.