Story of the game
It was clear from the early minutes of the game that Wednesday were more switched on for this match. They executed a quick tempo, passing the ball around with ease as the Birmingham players were unable to get close to their opponents.
Blues goalkeeper Neil Etheridge was tested in the opening minutes when he was called into action to parry Adam Reach's effort from outside the area.
The Owls constantly applied pressure to Birmingham's back four as they had completely overrun the midfield, with veteran midfielder Barry Bannan pulling the strings.
The hosts had a good chance to take the lead through Jeremie Bela, but the winger's effort from the right-side of the area was dealt with ease by Wednesday stopper Cameron Dawson.
However, it was the visitors who saw the best chances in the first period. Josh Windass's free-kick on the edge of the area rattled against Etheridge's left post before a wonderfully floated ball from Moses Odubajo was met by Callum Paterson whose header flew just wide of the post.
The way the Owls were playing and creating chances was telling that a goal was not far away. It came very early in the second-half when Bannan scored from the penalty spot after Paterson was adjudged to have been tripped by Adam Clayton.
Blues really struggled to apply any pressure in search of an equaliser for the bulk of the half, with Wednesday sitting comfortably with their narrow lead.
The real spark for the hosts was substitute and debutant Jonathan Leko. The youngster's pace and intricate play added some much-needed speed to Birmingham's play. They started to cause some problems for Garry Monk's side who started to be pegged back in the closing period of the game. Leko, along with forward Scott Hogan and the stalwart George Friend having great chances to level the score.
However, their late push for a goal was too late and Aitor Karanka's unbeaten start to the season had finished.
Man of the Match
The versatile Scotsman was excellent for the Owls today. Not only was he a nuisance leading Wednesday's line alongside Windass, he caused numerous problems for the hosts out of possession too. It was his natural instinct to get in front of Clayton to win the crucial penalty that provided his side the victory. His work rate offensively and defensively is commendable and pivotal in the Sky Bet Championship.
Wednesday should face no issues with retaining their Championship status this season. The performance they put in today will do them well going into this congested period before the next international break. Although Birmingham did not provide much of a contest for the bulk of the game, Monk's side will only grow with confidence after today's showing and could soon close down on the sides nearest them in the table.
As for Blues, their unbeaten bubble has been burst but they need to quickly forget about today's game ahead of Tuesday's trip to Carrow Road. They will need to be more aggressive and quicker in the way they play because they need to score from open play sooner rather than later.