Middlesbrough head coach Michael Carrick said:
"It's a horrible way to lose a game, especially a game of this significance and stature.
"To lose the game and concede those goals, an own goal and a deflection is difficult but we have to accept it.
"We started the game ever so well, went ahead, looked like we could add to that and were in a really good place. There was a two-goal swing which we dealt with well and we came back into it well, but we kind of drifted second half and didn't do enough.
"The form is not a concern, but we have to win games, there's no getting away from that."
Sunderland head coach Regis Le Bris said:
"Middlesbrough started very well, playing really good football. We conceded many situations so we were a little bit lucky not to concede a second goal.
"We stayed in the game, but it tested our patience as maybe we were a bit sloppy in possession.
"At half-time, we spoke about character, about playing with more passion. It was an intense game against a strong team and we had to play with 101%, not 80 or 85 or 90. And second half, we did that and we played a bit more vertical.
"This is a young team with talented players. It has a big margin, it is a question of how quick we can grow."