Amad Diallo made and scored one for Sunderland to deny Birmingham a place in the Sky Bet Championship’s top six with a 2-1 victory at St. Andrew’s.
On-loan Manchester United forward Diallo, who cost the Old Trafford club £20million when he signed from Atalanta, set up Ellis Simms to give the Black Cats a 25th-minute lead and then scored a superb second four minutes after half-time.
Substitute Lukas Jutkiewicz pulled one back late on for Birmingham.
Victory made it seven points from three away games for Tony Mowbray’s side and ended Birmingham’s six-match unbeaten home record.
But Blues could only blame themselves after wasting chances, with captain Troy Deeney heading against the bar at 0-0 and Scott Hogan missing a one-on-one at 1-0.
There were early chances for both teams in a lively opening.
Birmingham goalkeeper John Ruddy made a vital block from Simms from Dan Neil’s cross.
Blues responded with a glancing header from Deeney that hit the bar after Dion Sanderson nodded on Emmanuel Longelo’s cross.
But after serving warning of his intentions, on-loan Everton forward Simms, who was making his 50th league appearance, gave Sunderland the lead in the 25th minute.
It came after some brilliant tenacity and trickery from Diallo – but awful defending from Blues.
The Ivory Coast international beat Sanderson and Jobe Bellingham far too easily and even continued his run after being briefly grounded before putting Simms through to drill home powerfully on the angle.
Blues wasted a superb chance to equalise five minutes before half-time. Deeney played Hogan in for a one-on-one with Anthony Patterson but the Sunderland goalkeeper was quickly off his line to block well and deny the striker a 10th goal of the season.
Diallo appeared to put the game beyond Birmingham in the 49th minute. He raced onto a diagonal pass from Neil down the right and cut inside Auston Trusty before bending a superb left-foot curling shot into the far corner of the net with Ruddy motionless.
Birmingham were spared more punishment from Diallo when he departed in the 65th minute after Juninho Bacuna’s stray boot caught him in the face.
Jutkiewicz rewarded Birmingham’s pressure in the 78th minute. The veteran striker swept home Longelo’s cross from 15 yards after Sunderland missed the chance to clear.
City pounded Sunderland’s goal in the latter stages but after Patterson denied Sanderson, Hogan headed inches wide from Deeney’s cross.