Moments later the home side made the extra player count when alert winger Marcus Forss fired past Canaries keeper Angus Gunn.

Emmanuel Latte Lath doubled the lead just before half-time with a cool finish inside the box, before Lukas Engel secured all three points with a fine volley.

Defeat for Norwich temporarily stunts their play-off aspirations, and moves Middlesbrough up to 12th place.

It was the home side who created the first notable chance when Dimitris Giannoulis broke through the Norwich back line to force a save from goalkeeper Seny Dieng, with Sainz firing the follow-up wide.

But the Canaries broke the deadlock with Ashley Barnes latching onto a chipped ball from Gabriel Sara. Barnes fluffed his lines on the first attempt before poking home his fifth goal of the season with his second.

The turning point for David Wagner's side came after 30 minutes when Sainz's coming together with Howson prompted the referee to send him off.

Boro instantly made the extra player count when left-back Engel played a lovely weighted pass across the face of the Norwich goal for Forss to stab into the back of net, prompting a roar of relief from the Finland international.

Things went from bad to worse for Norwich when Middlesbrough's Matt Clarke whipped in a cross that the unmarked Latte Lath chested down before turning and coolly slotting the ball home.

Norwich, who started the evening within two points of the play-off places, found themselves under relentless pressure in the early stages of the second half when Riley McGree made a charging run behind the Norwich defence, forcing Gunn to save with his feet at the near post.

Middlesbrough asserted their dominance after 62 minutes when Luke Ayling's cross was met by a first-time volley from Engel, who fired his shot into the ground and over Gunn.

Middlesbrough manager Michael Carrick told BBC Radio Tees:

"We didn't start terrifically well and we were a little bit indecisive but I thought we got to grips with the game, and the sending-off made a difference.

"I thought we made the most of [the extra man advantage], because it's not a given because 10 men can be tricky, but I thought the boys approached it really well.

"I didn't see [the incident] so can't give an opinion on it, but there's no denying it was a big moment in the game.

"We were desperate to win the game tonight and get the reward to match the players' commitment."

Norwich manager David Wagner said:

"In the first half an hour, until the red card, it was one of our best away performances this season.

"We were very good in all departments, scored a wonderful goal, and had chances to score more.

"Was it a red card? I have my opinion and I think everyone knows what that will be, but it doesn't count. We may appeal it because if someone gets hurt we will be very short of [players].

"Hopefully if we do appeal we will be successful."