Arsenal were fortunate to be tied 1-1 at halftime. Birmingham took an early lead off a set-play, when 6'8" Nikola Zigic headed in off a set-play. Their lead easily could have been 3-0. Before Zigic's goal, Arsenal benefited from an incorrect offside call that prevented a good penalty claim by Birmingham's Lee Bowyer, and possibly a red card for Arsenal goalie Wojciech Szczesny. After Zigic's goal, Birmingham opened up the Gunner defense way too easily, and only a fine, point-blank save by Szczesny prevented another score. Finally, the Gunners regained some possession and started pressuring the Birmingham defense. The Gunners' goal came in the 39th minute, after Jack Wilshire - Arsenal's best player of the half by some length - struck the crossbar with a vicious shot from 30 yards out. Andrei Arshavin controlled the rebound on the edge of the box and worked his toward the goal line before crossing to Robin van Persie, who volleyed the ball into the Birmingham net. Arsenal could have scored again before the end of the half, when Samir Nasri hit a rocket from outside the box that Birmingham goalkeeper Ben Foster could only parry away. With the Gunners piling on the pressure, the Birmingham players were no doubt happy to hear the half-time whistle.
If Gunners' fans expected Arsenal to take over the game in the second half, they were disappointed. For the first few minutes after the break, Arsenal did look dangerous, but then Birmingham came back into the game with dogged determination. In fairness, Birmingham's team work-rate was higher than Arsenal's throughout the match. Unlike Arsenal, this was Birmingham's one chance for silverware this season, and they were going all out for it. Arsenal, by contrast, seemed to be treating the game as just one more in a congested schedule of fixtures. Nevertheless, as the second half wore on, one could sense tiredness creeping into the Birmingham players' legs, and Arsenal upped the pressure. As the half wore on, Birmingham goalie Ben Foster kept his team in the game, making several fine saves. As long as he managed to keep Arsenal at bay, Birmingham could hope to grab a victory at the death.
And they did - out of nothing. On a easy ball into the box, Szczesny and Koscielny got all tangled up, and took each other out of the play. The ball fell at the feet of Birmingham substitute Obafami Martins, like manna from heaven. Martins simply passed the ball into a gaping goal.
Arsenal outplayed Birmingham for much of this game, but this was not a lucky victory for the Blues. Birmingham thoroughly deserved it. They played harder and with greater resolve, earning the luck that gave them the win.