Gabby Agbonlahor climbed off the bench to score the winning goal for Aston Villa as Harry Redknapp's first game as Birmingham boss ended in a 1-0 derby defeat.So often the scourge of the Blues, Agbonlahor's introduction as a substitute just before the hour immediately brought life to an otherwise dour encounter.Making his return from a three-month lay-off with a hamstring injury, the 30-year-old was immediately in the thick of the action, getting involved in a scuffle with Ryan Shotton before being booked and showing his fists to the Birmingham fans.He then made the telling contribution in the 68th minute, just nine minutes after entering the action, when he turned the ball home for his first goal since February 2016.It was not the start Redknapp hoped for after this week agreeing to oversee Birmingham's remaining three Championship matches following the departure of Gianfranco Zola.The Blues stay one place and two points above the relegation zone and Redknapp has games against Huddersfield and Bristol City to fulfil his remit of keeping the club in the division. The afternoon began with Villa and Birmingham fans united to observe a minute's applause in tribute to Ugo Ehiogu, the former Villa defender who died this week aged 44 following a cardiac arrest. Both sets of players also wore black arm bands as a mark of respect. There was little love lost when the action began, with a robust tackle from Mile Jedinak on Maikel Kieftenbeld bringing the crowd to their feet.That was all there was to get excited about until late in the first half. The game's first real chance arrived in the 38th minute when Lukas Jutkiewicz crossed the ball for Che Adams but, with the goal at his mercy, the Birmingham forward steered his shot over the crossbar from 10 yards out.Villa responded before the break as Leandro Bacuna flashed a shot across the face of goal.It was similar fare in the second half as both teams continued to lack fluency. A fine fingertip save from Sam Johnstone to deny David Davis proved pivotal moments before Agbonlahor struck. It was a scrappy goal, much like the game, and the striker was in the right place at the right time to fire the ball into the roof of the net following some head tennis in the Birmingham penalty area as the visitors failed to clear their lines. Redknapp's side tried to engineer a chance to get the equaliser but the closest they came was three minutes from time when Davis flicked a header just wide. It would have been met with a sigh of relief from Villa and Wigan fans alike as a point for Birmingham would have relegated the Latics.