Fernandez, a former Real Madrid C midfielder, has a torn medial ligament but will not require surgery.
"The specialists are saying 10 weeks but knowing Marc and the determination he's got he's already telling me he's going to be early, but that's the sort of kid he is," said Rovers boss Paul Dickov.
Fernandez, 23, was Dickov's first signing as manager of the newly-promoted Championship club.
Real bought the defensive midfielder from Espanyol in 2009 before moving him on to CD Olimpic de Xativa in the Spanish equivalent to the Championship.
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