Middlesbrough head coach Michael Carrick admitted that Ryan Giles' 87th minute own-goal was a 'horrible way' to lose the Tees-Wear derby.
Boro had led 1-0 through Delano Burgzorg and pulled it back to 2-2 through Hayden Hackney's fine strike, but Giles' unfortunate contribution settled the match in Sunderland's favour.
Defeat keeps Boro in seventh, outside the play-offs on goal difference from West Bromwich Albion.
"It's a horrible way to lose a game, especially a game of this significance and stature," he said.
"To lose the game and concede those goals, an own goal and a deflection is difficult but we have to accept it.