Gaston Ramirez is available to make his first start for Middlesbrough since 2 January after returning from injury.
Adlene Guedioura is cup-tied and Antonio Barragan is out, but George Friend returns after missing three weeks with a calf problem.
There are no new injury concerns for Oxford, who have defender Joe Skarz available following illness.
Christian Ribeiro and Sam Long remain sidelined for The U's although in-form Kane Hemmings is set to start.
MOTD COMMENTATOR'S NOTES
Robyn Cowen: "Premier League survival remains the priority for Middlesbrough, so their increasingly tenuous position in the table might lessen their commitment to this fifth-round tie against Oxford United.