The left-back has given agent Jorge Mendes the go-ahead to find him a new club, with his name circulating among sides in England, Portugal and Italy.
A move to Manchester United is understood to excite the player most, though according to the Manchester Evening News, United are not the only English club with an interest in the 22-year-old.
Hansi Flick had made clear on Saturday that he wants players fully committed to the cause, and followed through on Sunday by naming a squad without Balde.
João Cancelo, who can operate on either flank, and academy product Pesquer travelled in his place, with competition from the Portuguese international the central reason behind Balde's apparent change of heart after a summer spent insisting he wanted to stay.
Manchester United's need for a left-back is pressing, with Luke Shaw entering the final year of his contract, Diogo Dalot and Noussair Mazraoui both naturally right-footed, and Patrick Dorgu having been redeployed further forward.
United have already made contact with Mendes over Balde, though the club are said to be weighing a considerably cheaper alternative in Jorge Salinas of Racing Santander, whose release clause sits at around £16 million, with Racing sporting director Chema Aragón publicly acknowledging the clause could open the door to a sale. The gap in cost explains why United have so far monitored Balde's situation without submitting a formal proposal.
The only concrete proposal to reach Barcelona so far has come from Benfica, though it falls well short of the club's valuation.
Aston Villa are seen as the best fit for the figures Barcelona have in mind, though their spending power depends on offloading players of their own first. Barcelona, who need to create financial room elsewhere in the squad, have no intention of selling the 22-year-old cheaply, having valued him at around €40-45 million only a few months ago.
With the departure now appearing increasingly likely, Barcelona's sporting department has already begun searching for a replacement left-back. Without Balde, the left flank would be left in the hands of Cancelo and Gerard Martín, a threadbare option for a long season.