Virgil van Dijk admitted Liverpool's troubled season has been "unacceptable" after a 3-2 defeat at Manchester United dented their push to qualify for the Champions League.
The Reds' loss against their bitter rivals on Sunday left them in fourth place in the Premier League.
Arne Slot's side, crowned champions 12 months ago, have mounted a dismal title defence, forcing them to settle for fighting to reach next season's Champions League.
After their 18th defeat in all competitions this term, Liverpool still need four points from their remaining three games to seal a place in Europe's elite club competition via a top five finish.
Slot was without star forwards Mohamed Salah, Hugo Ekitike and Alexander Isak, as well as two goalkeepers, through injury against United.
But Liverpool captain Van Dijk conceded fitness issues could not be used as an excuse for such a turbulent campaign.
"I'm not here to make excuses. It's been a very disappointing season, an unacceptable season for us, and it's tough," he said.
"We shouldn't feel sorry for ourselves whatsoever. We have to work, we have to turn this around and make sure that next season these things don't happen because it's not Liverpool."
Van Dijk hit back at criticism of Liverpool players' use of their free time after several were pictured abroad before the United game.
"I'm not sure it's a holiday. It's a city trip," the Dutch defender said.
"But I think if you have one day off, and you don't have many days off, they decide what they want to do with their families. We are not kids. Everyone is an adult."
Put to him that some critics believes the team has too much time off, Van Dijk said: "Really? I wish we had a couple more days off at times because I think it works both ways.
"You see Pep Guardiola giving (Manchester City) three days off, for example, the last weeks in a row and they are doing pretty well. It is finding the right balance."
Slot is under fire for failing to keep Liverpool in the title race in a season that will end without silverware.
And Van Dijk, who has won the Premier League and Champions League during his time at Anfield, is determined to ensure Liverpool don't endure a repeat of their frustrating form next season.
"Like anyone else, obviously, personally I want this to be solved. I want us to be what I've experienced over my time here. I want to be successful," he said.
"Consistency is the most difficult thing in any job, in anything you do, but it is the best way to get results and also be successful. That's what we have to try and find.
"We have to realise that next season we can't repeat (this). It's unacceptable."