The former Brazil striker fears the Camp Nou side could miss out on the top four in La Liga unless they turn things around soon
Barcelona must drastically improve under Ronald Koeman if they are to save their season, says former star Rivaldo.
The Catalan side are through to the last 16 of the Champions League, but lost 3-0 at home to Juventus in the final game of the first round to finish second in the group.
They have underperformed domestically, too. Koeman's team sit ninth in La Liga and are 12 points behind leaders Atletico Madrid, having won just two of their last eight matches in the competition.
Rivaldo fears the Camp Nou side are far off the quality required to challenge for the European title this term and fears they could even miss out on next season's competition unless they turn things around soon.
"For now, I'm not seeing Barcelona producing enough football to fight for the Champions League title this season, but things can change if they manage to knockout a strong opponent in the last-16 as it would boost their confidence," he wrote in a column for Betfair.
"Many are starting to doubt whether Barca can claim a top four spot at La Liga in order to take part in the Champions League next season.
"If they keep under-performing then that is a real possibility. The team isn't playing well, and things are getting uglier.
"It's crucial that they wake up as soon as possible and get back to producing good performances and results."
He added: "At the end of Juventus match, Antoine Griezmann didn't find many excuses for their loss and blamed all the group for their lack of attitude on the pitch. I think he was right on his claims.
"You must be fully committed when playing in a Barcelona shirt - full of history and glory - but that isn't happening now, which I consider unacceptable. It's not normal to watch Barcelona losing 0-3 at home in an important match."
One of Barca's biggest worries is the future of superstar Lionel Messi, who is in the final season of his contract and has shown no signs he is willing to sign a new deal.
Atletico Madrid star Koke has spoken about how he would love to persuade Messi to join his side, but admitted it would be difficult “for him to get out of there.”