Douglas has completed a season-long loan move to Portuguese champions Benfica as Barcelona continue to reduce the size of their squad before the close of the transfer window.
Barca had hoped to be able to sell Douglas this summer, but in the end have had to settle for a temporary deal.
The club have not made it clear if Benfica have an option to buy the right-back at a later date, but reports in the Catalan press suggest there is an obligatory purchase written into the agreement if he plays a certain amount of games.
Douglas, 27, joined Barca from Sao Paulo in 2014 for €5 million but has failed to make an impact in his three years at Camp Nou.
Despite being part of the squad that won the Treble and then the double under Luis Enrique, he made just eight appearances in all competitions in his first two years with the club.
He spent last season on loan at fellow La Liga side Sporting Gijon, who were relegated, and returned to Barca in the summer, joining the club's tour of the United States.
Like Douglas, Sergi Samper and Marlon Santos have also left Barca on loan during the transfer window and the club are still hopeful of moving on more players.
Munir El Haddadi has been linked with a transfer to Torino and Andre Gomes is close to completing a move to Premier League side Tottenham Hotspur.