Rotherham's Stephen Brogan was taken to hospital after sustaining a double fracture of his lower leg in Saturday's 1-1 draw at Milton Keynes Dons.
Brogan was stretchered off after 55 minutes at Stadium MK
The 19-year-old utility man was stretchered off after a collision with Dons goalkeeper Willy Gueret.
"Once the lad broke his leg, it took the tempo out of us," Milton Keynes assistant boss Ray Mathias said.
"It affected the players - Willy was heartbroken in the dressing-room, so it shows you the severity of it."