The 22-year-old was taken off following a robust challenge by Radja Nainggolan during Barcelona’s 1-1 draw with Roma during the week.
Rafinha has suffered a tear to the anterior cruciate ligament in his right leg and has been ruled out for long spell on the sidelines. The Spanish international is set to undergo surgery in the coming days and according to Spanish website Sport.
The Express states that Barcelona are preparing a move for Gündoğan in January when their transfer embargo ends.
Dortmund rejected an approach from United for Gündoğan according to the German newspaper Express.
Gündoğan recently signed a contract extension with Dortmund however, he has recently also been linked with a move to Juventus.
The 25-year-old wrapped up last season with five assists and three goals in 33 appearances in all competitions.