Derby defeat for Black Cats.
Sunderland suffered a derby defeat on Wearside as Middlesbrough progressed to the last eight of the Capital One Cup.
A goal from Scott McDonald just before the break proved to be the decider and the Black Cats can have few complaints about the result.
Boro, who registered their fifth straight win, acquitted themselves well on the night and deserved their victory.
Sunderland started brightly but the visitors soon established a foothold in the game and capitalised when McDonald turned in Ishmael Miller's cross.
Boro lost a lead at the Stadium of Light last season but there was no way back for Sunderland this time.
Manager Martin O'Neill made five changes to the side that drew at Stoke and reverted to a two-striker system with Louis Saha partnering top scorer Steven Fletcher up front.
Adam Johnson, playing against his former club, saw a cheeky inswinging corner almost sneak in at the near post after just two minutes only for keeper Jason Steele to punch the ball away at the last moment.
The ball eventually found its way to Saha at the back post, but the striker saw his shot fizz through a crowd of players and over the bar.
Tony Mowbray's side, though, settled into their assignment and began generating attacking threats, with Faris Haroun drawing a good block from Keiren Westwood before McDonald cleared the crossbar with a speculative effort from 25 yards.
The visitors should have been ahead courtesy of a lightning break 23 minutes in as left-back George Friend found Miller in space, but the striker was left holding his head in his hands as his weak shot from 12 yards trickled harmlessly into Westwood's arms.
And Boro's momentum was definitely building as McDonald clipped the top of Westwood's crossbar with a cheeky chip after the busy Miller lost possession.
The forward had already come close on two occasions – and he didn't waste his third sight of goal to give the away side the lead six minutes before the break.
Miller carved a path down the right with a strong run, crossing low for McDonald to cut across his marker and clip the ball beyond a helpless Westwood at the near post.
Fletcher came closest for Sunderland in the latter stages of the first half, pulling away at the back post to meet Johnson's cross with a downward header which Steele dealt with comfortably.
There was just no way through for O'Neill's side with the visitors looking to break forward and exploit space at every opportunity.
Stephane Sessegnon's quicksilver run and shot just wide gave Sunderland a lift on the hour, but Boro quickly reasserted themselves to shut the game down.
Indeed, the margin of victory was almost increased with Westwood forced to make good saves to deny McDonald and Haroun, while Friend fired over on the turn when he really should have done better.
The visitors held their breath with time running out when defender Andre Bikey nodded Sessegnon's cross towards his own goal, but the ball drifted harmlessly wide of the far post for a corner.
And it was Sessegnon who came closest to fashioning an equaliser late on, gaining a yard of space at the back post only to head into the side-netting.
- Johnson (Campbell)
- Saha (McClean)
- Hines (Parnaby)
- Ledesma (Reach)
- McDonald Yellow
- Miller (Smallwood)