Tony Capaldi made his comeback for Oxford's reserves as they went down 1-0 at Southend on Tuesday afternoon.
The experienced defender is yet to make a first-team appearance for the U's since his arrival last summer having struggled with a host of injury problems since pre-season.
But Capaldi returned to training two weeks ago and played the first 45 minutes at Roots Hall before being replaced without any ill-effects.
Trialists Lewis Stockford and Umpha Koroma, from Portsmouth and Stoke respectively, also started, as did the likes of Wayne Brown, Damian Batt, Tyrone Marsh and Harry Worley in what was a largely youthful XI.
Oxford were sunk by an 87th-minute winner by Southend trialist Rowan Vine.