Greg Halford's leaping second-half header against Preston was enough so send Sheffield United through to the play-off final.
Blades seal Wembley passage
Greg Halford's leaping second-half header was enough so send Sheffield United through to the play-off final at the expense of a battling Preston side.
The Blades beat their promotion rivals 1-0 at Bramall Lane (2-1 on aggregate) thanks to a solitary strike from the on-loan Sunderland defender.
Halford left the pitch minutes later when damaging his Achilles after an awkward landing but will be hoping to return for the final at Wembley in a fortnight.
Preston threw everything at United in the final 20 minutes despite failing to cause any real impact before conceding.
Their late surge came to nothing, though, as they crashed out of the Championship play-offs in their eighth campaign.
Blades manager Blackwell was forced into two changes from the side that started the first leg.
Strikers Jamie Ward and Darius Henderson were ruled out through injury, so David Cotterill and Craig Beattie stepped up, the latter up front on his own.
Preston's Alan Irvine made a double tactical switch, with Chris Brown and Barry Nicholson, both second-half substitutes at Deepdale, starting in place of Neil Mellor and Darren Carter respectively.
Preston pair Ross Wallace and Jon Parkin were both booked in a high-octane first half packed with tension but low on chances.
Wallace was first into referee Alan Wiley's book for his lunging challenge on Nick Montgomery and Parkin was lucky to avoid a straight red for his studs-up tackle on Halford.
The Blades shaded the first period with Brian Howard and Nick Montgomery outstanding in midfield, but while Cotterill and Kyle Naughton peppered the Preston penalty area with crosses, the final ball eluded lone striker Beattie.
Preston midfielder Nicholson rifled a 20-yard shot over the crossbar and Wallace cracked a free-kick against the wall, but the Blades carried the greater threat going forward.
Howard drove wide in the 25th minute and Halford's rising shot was also off target, while Chris Sedgwick blazed over at the other end.
The Blades came within a lick of paint from the opening goal five minutes into the second half when Howard's deft flick teed up Beattie, whose low drive shaved Preston goalkeeper Andy Lonergan's post.
Beattie then forced Lonergan into a fine one-handed save with a downward header from another Cotterill cross.
But Preston cracked under the deluge. Cotterill was again the supplier on the right and Halford rose highest to guide a superb header beyond Lonergan and into the far corner.
It had taken the Blades an hour to break the deadlock, but the visitors almost levelled it up three minutes later when Billy Jones' raking drive was parried by home goalkeeper Paddy Kenny.
Preston's response was immediate and they enjoyed a period of sustained pressure.
Irvine sent on Mellor and Carter in the 72nd minute, but moments later Beattie almost doubled the Blades' advantage when his shot was blocked by Preston defender Sean St Ledger on the goalline.
Moments later the sprawling Montgomery kept out Jones' low shot in similar fashion.
Blades midfielder Stephen Quinn was thwarted by the on-rushing Lonergan in the 86th minute and although Wiley played four minutes of time added on, the home side held firm and await either Burnley or Reading, who play in the second semi-final.