Oxford’s on-loan Liverpool forward Ben Woodburn has been ruled out for three months with a fractured metatarsal.
The 19-year-old limped off early in United’s 2-2 draw at Accrington on Saturday.
“It’s such bad luck for Ben because he has been showing everyone what a good player he is, and now he’ll be out for 12 weeks or so,” manager Karl Robinson told oufc.co.uk.
“He came in today with a cast on his ankle and foot and we had a chat; he is a great lad and will listen to the advice and he is determined to keep doing what he can and come back fitter and stronger than ever.
“It is now up to other players to show what they can do in his absence.”