The Blaugrana legend saw Luis Suarez leave Camp Nou over the summer, while Ansu Fati has suffered an injury, making reinforcements essential
The Blaugrana took in a troubled summer which was dominated by high-profile departures and rumours regarding other possible exits.
Quique Setien was relieved of his managerial duties, while experienced frontman Luis Suarez was offloaded to Atletico Madrid once Ronald Koeman took the reins.
Barca were able to prevent talismanic captain Lionel Messi from jumping ship, but he is only tied to a contract through to the end of the season.
After fighting so many fires, and with funds in short supply during the coronavirus pandemic, there was little movement into Camp Nou.
Koeman still has a star-studded squad at his disposal, but his options have been depleted by an unfortunate injury to teenage prodigy Ansu Fati.
With the 18-year-old ruled out while Messi and Antoine Griezmann seek to recapture top form, Rivaldo believes additions have to be made over the winter in order for Barca to be competitive.
The Blaugrana legend told Betfair: “I thought Barcelona should sign someone before Ansu Fati’s injury, so now I think it even more.
“The club should try to sign one or two strikers if they want to fight for the Champions League.”
The Brazilian added: “Koeman should have more options in attack to manage a line-up which is sufficiently decisive and competitive in big games, in important ties.
“Ansu was playing well, he was gaining confidence and becoming more influential in the team, his absence is another headache for the coach.”
Cut-price deals will be sought at the turn of the year, with there still a couple of options that Koeman and Co are prepared to consider.
Manchester City defender Eric Garcia is wanted back in his native Catalunya, as his contract at the Etihad Stadium runs down, while Dutch forward Memphis Depay would bolster the attacking ranks.
Lyon, though, are reluctant to part with the Netherlands international mid-season and it may be that Barca have to make do in their domestic and continental campaigns through to the end of 2020-21.