Holding a 1-0 lead at halftime, Betis collapsed to lose 4-1 in Wroclaw on Thursday night.
At the final whistle, captain Isco said: “It hurt at the end because it was such a heavy result. Football is unforgiving, and despite having a good first half in which they barely had any chances, they completely overwhelmed us in the second. We didn't know how to take advantage of the score, something that happens to us all season. Today was a night like that.
"Despite what was said in the locker room, they had plenty of options and they've turned it around."
To the fans, he added: “Thank you. We're so sorry we couldn't give away this title. What these fans give us fuels us to keep trying next year. We owe them one, and we're going to give it to them.”
The season is worthless now
Meanwhile, defender Marc Bartra also said: "They've had more attacks from the wings. Both times they've had shots on us, it's been a goal. It's hard to swallow.
“To all the Betis fans and our families who have supported us since the beginning of the season. This is a sport, and the final is all or nothing. It's a source of pride to see them like this, despite the defeat. I love this club because of the way they cheer us on at every stadium, and that says a lot about the club.”
On their season, Bartra added: "It seems like it's worthless now, and we'll appreciate it as time goes on."