O'Neill played in the centre of defence, perhaps with a view to Saturday, and headed the opener on 15 minutes but it was Sunderland who went on to win the game, equalising in the 56th minute with a good finish before scoring a brilliant winner twenty minutes from the end.
Burnley used five substitutes in a game that saw Aryn Williams wear the claret and blue for the last time, playing the full 90 minutes at right back.
Jack Errington came on for the last half hour to cement his return following heart surgery having featured in a youth team friendly last week, his first action since playing at Alfreton in pre-season.
The team today was: Trialist, Aryn Williams, Archie Love (Jack Errington 61), Alex Coleman, Luke O'Neill (Tom Anderson ht), Steven Hewitt, Luke Gallagher (Nathan Lowe 71), Trialist, Cameron Howieson (Jason Gilchrist 75), Trialist, Wes Fletcher (Shay McCartan 79). Subs not used: Callum Jakovlevs, Joe Jackson, Trialist.