Barcelona boss grabbed a 6-1 win over Deportivo Alaves over the weekend as he played Joao Cancelo at left-back and handed Brian Farinas a start at right-back, snubbing Balde once more.
The Spanish champions have won all three games in the UEFA Champions League with 12 goals scored in the competition as they next come up against Aston Villa, a game where Balde will likely remain on the bench once again.
Reports suggest Barcelona could allow the 22-year-old to leave after he fell down the pecking order under Flick, who has deemed him surplus to requirements.
According to Fabrizio Romano's reporting, United contacted Barcelona during the summer, but the deal was difficult to complete.
However, with a meeting set to take place with Lisandro Martinez this week regarding his shaky future, Balde could be an interesting replacement for the World Cup winner whose deal expires in 2027.
Reports in Spain state that Balde, an academy graduate, is increasingly open to leaving in January after struggling to secure regular playing time.
With Martinez potentially set to leave, the door could open for Balde to step into the United side who are close to the relegation zone following their defeat to Chelsea over the weekend.
Managing just 101 minutes in La Liga and 16 minutes in the Champions League, Balde may be tempted by the move as United clearly value him much more than Barcelona.