First, on the half hour, he was booked for a challenge on Grady Diangana and then, after having an effort denied by Albion keeper Alex Palmer, on 33 minutes, he waved an imaginary yellow card of his own towards referee James Bell.

But Bell responded by waving the real thing back at him - which meant a second yellow, Sainz red-carded and Norwich having to play out two-thirds of the game a man short.

Despite being overwhelmingly the better side throughout, it took until five minutes into the second half for the Baggies to break through.

Another tempting right-wing cross from home skipper Jed Wallace was met by Diangana, who headed down for Thomas-Asante - and the potential Africa Cup of Nations striker prodded home his seventh Championship goal of the season to end the Canaries' five-game unbeaten run.

Borja Sainz's first booking was for his 30th-minute challenge on Grady Diangana

Albion had won four of their previous seven league games against Norwich, including a 2-1 victory in their most recent meeting in April.

The Canaries had also lost in their four most recent Boxing Day fixtures, having had not won since a 2-0 victory in the Midlands, at Birmingham City, in 2017.

But, in a game the Baggies were already dominating, the Canaries' task of upsetting the form book was further loaded against them by the loss of Sainz.

It remained one-way traffic as the busy Wallace created openings for Diangana, a chip from John Swift and Darnell Furlong - efforts which all went wide.

But home keeper Palmer had to remain alert and, late on, he made a vital one-handed save from Norwich substitute Hwang Ui-jo to preserve all three points for Albion.

Who's next?

Albion are at home again on Friday (20:15 GMT) when they host Leeds United in a meeting of fifth against fourth.

Norwich are again on their travels (19:45), also on 29 December, when they go to Millwall.

West Bromwich Albion head coach Carlos Corberan:

"On one side, yes it changed the game and cost us the game.

"But, on the other side, it doesn't mean that you are automatically not without a chance.

"The result was fair, from the way the game was going against 11 players and the way it went when we were against 10.

"I know the group wanted to take responsibility when they think something has not gone well and we never want to make excuses."

Norwich City head coach David Wagner:

"When you're on a booking, you can't ask for another yellow. Everyone knows this. This rule exists all over the world.

"So it's something you can't do, especially if you've been booked and this is why - even if it's a harsh decision - it was the correct decision.

"There is no one to blame but Borja himself. I have to speak with him and I will do, for sure, but officially and not in public. We'll support him but it's my job to speak about the truth as well.

"If he takes what's right out of this situation - and I'll make sure he takes what's right - it will be another step in his progression."