Goals from Geoff Horsfield and Martin Grainger clinched the Blues a two-legged meeting with Millwall in the Division One play-offs.

Horsfield and Grainger struck within the space of two minutes just after the hour to seal the three points, despite Darren Purse being sent off for a professional foul with 13 minutes left.

The Blades fought bravely for the first hour keeping an increasingly anxious home side at bay.

Former Blues player Peter Ndlovu forced the first save out of Nico Vaesen when he turned just inside the area to shoot following Rob Ullathorne's penetrating cross.

Grainger and Horsfield then had their first opportunities to break the deadlock but both could not find the back of the net.

Soon after Stern John skipped onto a long through pass to beat Shaun Murphy and keeper Tracey to the ball but the striker's low cross was finally cleared by Murphy.

The turning point of an error-ridden game arrived when Steve Bruce decided to put on Damien Johnson and replace Paul Devlin on the hour.

Within a couple of minutes the game's outlook had completely altered.

Horsfield broke the deadlock just after the hour when he prodded home from close range after Hughes had gone in bravely.

Within two minutes Birmingham were on course for the play-offs party when Grainger curled in a left-footed free-kick inside Tracey's left-hand post.

Purse was then dismissed by referee Phil Richards for pulling down Blades substitute Nick Montgomery after 77 minutes.

But it did not matter as Birmingham's fourth successive trip to the play-offs had already been secured.

Birmingham: Vaesen, Kenna, Purse, Tebily, Grainger, Devlin, Bryan Hughes, Carter, Mooney, Horsfield, John.
Subs: Bennett, Lazaridis, Andrew Johnson, Damien Johnson, Vickers.

Sheff Utd: Tracey, Doane, Murphy, Page, Ullathorne, Javary, Jagielka, Tonge, Smith, D'Jaffo, Ndlovu. Subs: Montgomery, Cryan, Nicholson, Lovell, de Vogt. Referee: P Richards (Preston)

Attendance: 29,178