Axel Witsel has urged Borussia Dortmund to come back stronger next season after they closed the Bundesliga campaign with a 4-0 hammering at home to Hoffenheim.
Andrej Kramaric netted four times for the visitors as they booked a place in the Europa League qualifying rounds, while Dortmund, already sure of the runner-up spot, slipped to 13 points behind champions Bayern Munich.
Dortmund's humiliating end to the season did not sit well with Belgium international Witsel, as he criticised his team-mates for their poor defending.
"There is nothing to explain. They were more aggressive, had more motivation. We didn't want to end the season like that," he said to Sky Sport.
"It wasn't enough without a ball. We all have to defend together. If only a few players run and defend, it's difficult to win a game.
"We may be the better team on paper, but it is different on the field."
Looking back on the season as a whole, Witsel says there is room for improvement from his side.
"We had ups and downs in the first half of the season. The second half was better, but of course we can do it better," he added.
"Next season we will start the fight with [Bayern Munich] again."
Dortmund goalkeeper Roman Burki was also critical of the team and believes they lack the winning mentality required to challenge Bayern to the title.
"Already after the first 45 minutes you noticed that there was a team on the pitch that wanted it - and a team that didn't feel like it," he said.
"That shouldn't be. It's a Bundesliga game. We should all be happy that we can play here. A lot of things were wrong and then the result is what it is.
"Maybe we just sometimes have the wrong mentality. We have to work on our winning mentality, Bayern have it more than we do.
"It is precisely these points that we are missing in the end to be at the top.
"I have not won against Bayern many times and I can only explain that by not having the right attitude or mentality."