After an even first half, Black Cats midfielder Dan Neil was shown a second yellow card for dissent as the hosts were reduced to 10 men.
Middlesbrough then took full control after their interval as Sam Greenwood and Matt Crooks both scored in the space of three minutes.
The visitors then added a third when Isaiah Jones broke down the right and converted with a calm finish, before a last-minute goal from Marcus Forss.
Here’s how Phil Smith rated the Sunderland players at the Stadium of Light:
1. Anthony Patterson - 7
Made some brilliant stops and was very unfortunate to be on the receiving end of such a scoreline. One save from Crooks early in the second half was exceptional. 7 Photo: Frank Reid
2. Trai Hume - 5
A solid first half, switched over to the left after Huggins’ injury and one of manu to find it tough as Middlesbrough worked their overloads with the extra player. Tough afternoon. 5 Photo: Frank Reid
3. Dan Ballard - 7
One of the Sunderland players to come out of the game with credit. Made some brilliant blocks and defensive contributions even as his side crumbled against a good side with ten men in the second half. 7 Photo: Frank Reid
4. Luke O’Nien - 5
Worked the ball well for much of the first half, struggled in the second as Middlesbrough carved out chances on a regular basis. 5 Photo: Frank Reid