The Reds trailed 3-1 with 20 minutes remaining, but struck twice to ensure an unbeaten pre-season campaign and stretch Ole Gunnar Solskjaer’s unyielding record as manager.
Against a Brum side containing first team regulars like Cameron Jerome, Marcus Bent and Gary McSheffrey, United’s young side were posed plenty of questions, and found themselves a goal down inside three minutes.
David Gray, operating at centre-back for the evening, was perhaps harshly adjudged to have taken out Jerome inside the area, and McSheffrey beat Tomasz Kuszczak from the spot to put the hosts ahead.
Quarter of an hour into the game, United drew level. Rodrigo Possebon bagged yet another scorching goal, this time hammering home a 30-yarder that gave Brum goalkeeper Dean Lyness no chance.
Shortly before half-time, Jerome restored the hosts’ advantage with a stunning shot of his own, and then converted a fine McSheffrey cross just before the hour mark to seemingly put the game beyond United’s reach.
However, having come back from two-goal deficits against Oxford, Northwich Victoria and Chelsea already in pre-season, the Reds have shown great resilience under Solskjaer’s reign, and grit was again on show at St Andrews.
Gray atoned for his earlier penalty concession by heading home Sam Hewson’s right-wing corner, before Evandro Brandao smashed home a superb low shot from the edge of the area five minutes from time.