Birmingham slumped to a 3-1 defeat at the Riverside Stadium on Sunday and while Blues manager Chris Hughton said his side was sluggish, Tony Mowbray praised the impact made by his substitutes.
Blues Adam Rooney had put City in front from the penalty spot, but Barry Robson smashed home a free kick to begin the fightback.
Belgian Faris Haroun came on as a sub and score on his debut to put the home side in front.
Then another new Boro signing, Frenchman Malaury Martin, also score on his debut after coming on as a sub and the game was then beyond the reach of Blues.
'It is nice to able to bring quality off the bench instead of relying on youngsters,' said Mowbray.
'For a lot of games while I've been here it has been a case of putting teenagers on the bench but we are getting to the position now when I can replace quality with quality and that helps.'
Martin sealed the victory with a 28-yard strike.
'He has been doing that in training,' Mowbray added.
'He cuts in and unleashes and a lot of them are unstoppable like the one we saw.
'It was nice for that pair to get off the mark with goals but it was especially pleasing as a team that we worked hard, we didn't rush it and we battled back to take an important three points.'
Birmingham boss Chris Hughton pointed to his own bench as he explained City's sluggish second half display.
'Legs were tired in the second half, possibly because we had a difficult game on Thursday night in the Europa League,' he said.
'But also we have lost three important players this week - Liam Ridgewell, Morgaro Gomis and Jordan Mutch - and that has left us with kids on the bench and unable to change it too much.
'In the first half we did well enough but in the second we tired, although we added to our own downfall by giving away a soft goal so early in the second half. There was no need to give away a free-kick there. That gave Boro the momentum.
'Was there a touch of offside about their second goal? Maybe, it was certainly very close. It was a fortuitous rebound for him.
'And we should have had a free-kick for a foul on David Murphy in the build up for the third but these things happen.'