Tony Pulis was disappointed that his Middlesbrough side did not subject Birmingham to a heavier defeat at the Riverside.
Britt Assombalonga’s 13th-minute goal gave Boro the points, following up Tuesday’s 3-0 win against Sheffield United, and they would have matched that scoreline had they been better in front of goal.
Both Assombalonga and Stewart Downing hit the post, and Jonny Howson had an effort cleared of the line.
“I thought it was a game that we could have won and should have won by five or six goals,” said Pulis.
“The chances and opportunities that we created were absolutely outstanding. I think we’ve hit the bar twice, we’ve hit the post twice, we’ve had one cleared off the line.
“There’s been a melee a couple of times where it could have easily dropped for us. Jonny’s missed a chance because Stewart’s got in the way, Stewart’s missed a chance because Jonny’s got in the way.
“We’re waiting for the whistle at the end but really and truthfully the game should have been buried.”
The win means Middlesbrough remain unbeaten, having drawn 2-2 at Millwall on the opening day, though Pulis remains frustrated not to have added new players to his squad on deadline day.
He added: “We’ve done fantastic to play three games in a week and three very competitive games and to have the energy that we’ve shown was a huge credit to the players.
“The lads have been fantastic in the three games but, being perfectly honest with you, the squad is not strong enough to maintain this, just ain’t strong enough. You can dress it up anyway you want to dress it up but I’d rather just be straight and honest with people and let them know how I feel.”
Boro are hoping to make loan signings of Everton pair Yannick Bolasie and former loanee Mo Besic, who almost joined them on a permanent deal on transfer deadline day.
Garry Monk, on his Riverside return having managed Middlesbrough for the first half of last season, was left to admit his team were fortunate not to concede more than one goal.
He said: “There was a lot of endeavour and fight and commitment but it is a league that demands you be on your game from the start and, especially away from home against one of the better teams with the demands on them to get promotion, you have to be on your game and in the first half we were not.
“We caused our own problems. It was 1-0 and they could have maybe scored another to be honest.”
Birmingham’s Craig Gardner was sent off in the closing stages for a challenge on Howson but the Blues may appeal against referee Andrew Madley’s decision.
Assombalonga’s goal came when he curled the ball home from the left side of the penalty area with his right foot.
It took a slight deflection off visiting right-back Maxime Colin, enough to take it away from goalkeeper Connal Trueman.
Assombalonga had another chance, Michael Morrison flinging himself at the ball to block the shot.
Boro were better all over the pitch, smothering any attacks that came their way and again they went close when Downing struck the inside of the post with a 20-yard free-kick.
The second goal Boro merited should have come just before the break, but this time Assombalonga hit the post after latching on to Martin Braithwaite’s back-heel.
During the early stages of the second half came a rare chance for Birmingham. Kristian Pedersen’s cross was headed towards goal by striker Lukas Jutkiewicz, but Darren Randolph pushed it wide.
At the other end there was a clanger by Trueman that almost cost his side a second goal.
He misjudged Shotton’s long throw and the ball bounced back off the underside of the bar with the goalkeeper able to claim it at the second attempt.
Boro then missed two more chances in quick succession. Howson created space but saw his shot cleared off the line by Morrison and, with Birmingham unable to clear, Howson headed across goal for a stretching Assombalonga, who poked wide.
Middlesbrough: Randolph, Fry, Flint, Friend, Clayton, Shotton, Wing (Tavernier 77), Howson, Downing, Braithwaite (McNair 89), Assombalonga (Fletcher 81). Unused substitutes: Konstantopoulos, Leadbitter, Johnson, Chapman.
Birmingham City: Trueman, Colin, Morrison, Dean, Pedersen, Jota (Solomon-Otabor 76), N’Doye, Craig Gardner, Maghoma (Mahoney 76), Adams (Bogle 70), Jutkiewicz. Unused substitutes: Camp, Roberts, Kieftenbeld, Harding.
Referee: A Madley (West Yorkshire).