The victory increased the daylight between the Blues and the Sky Bet Championship relegation zone, something Karanka wants to ensure keeps widening.

"I am very pleased with this performance. I hope this is a real sign of the future," said Karanka.

"We played well today for 45 minutes and then had to defend. We knew we had to defend really well against a good team and we did.

"We have shown we are a good team with the ball and without the ball, we hope this is a sign of what is to come.

"It's a nice feeling to have today because the biggest challenge here has been changing the atmosphere. I thought I'd fixed it earlier in the season but it's been the same situation. It will be really important for sure."

Former Middlesbrough defender George Friend was excellent as part of a well-drilled Birmingham backline that kept the home side at bay. Karanka took him to St Andrew's from Boro in the summer.

The Birmingham boss added: "George was a little sad because he was so good, he is almost blaming himself because he liked it here. He is a top man.

"When I signed him I knew I wasn't signing just a player, I was signing him as a top man off the pitch too.

"We defended well. The main thing is we knew the mistakes we were making before today.

"If you don't know the mistakes then that's a bigger problem. We know them so we can fix them. We have played, improved, but this is just one game."

Middlesbrough manager Neil Warnock was clearly less impressed because his side missed out on a chance to climb into the top six.

He was also annoyed that Birmingham's Ivan Sanchez was not sent off for kicking out at Paddy McNair in the first half, but Warnock felt the performance was not to Middlesbrough's recent standards.

Boro failed to hit top gear after the training ground had been closed down to the first team because of a Covid-19 outbreak.

"It's disappointing, and it's not very often I have a go," said Warnock. "First half we weren't good enough, we have one or two excuses but it wasn't good enough.

"For two or three of the lads that was their first session yesterday and we couldn't get on grass because of a frozen pitch. We didn't train until Wednesday either, two weeks of hell really.

"That doesn't stop you competing against a team like that, but you expect the referee to handle it. Sanchez has lashed out, four of them looking at the game, surely one of the four can see it. They can see a foul throw but can't see them lashing out? To make matters worse Sanchez made the goal.

"I will give them an excuse today but there are no excuses now. We are into the rest of the season, Saturday-Tuesday for the foreseeable now. It was a wake-up call in that respect."