Stags were dealt a massive blow ahead of the game with the news that striker Liam Hearn has been ruled out until after Christmas.
Scans revealed Hearn tore cartilage during the incident which forced him came off in the Capital Cup defeat against Sheffield United.
But there was better news with Ollie Palmer taking a place on the bench after it had been initially feared that he would be out injured for three weeks.
Cox chose to play former Oxford United trainee Alex Fisher up top with Sam Clucas the lone man in support.
John Dempster came in to captain Mansfield Town to replace Martin Riley, who also picked up an injury against Sheffield United.
Former Mansfield Town favourite Johnny Mullins lined up at the heart of the Oxford defence
Mansfield Town (3-5-1-1): Studer, Beevers, Sutton, Dempster, Tafazolli, Taylor, McGuire, Clements, Heslop, Clucas, Fisher. Subs not used: Jones, F, Bell, Marsden, Palmer, Thomas, Murray, A. Bell.