The 23-year-old striker, who dumped the Black Cats out of the competition in the fifth round last season with a twice-taken penalty and redeemed himself in the fifth round this year with an extra-time double in a replay at Birmingham, settled a tense tie with a superb 15th-minute effort to leave the Wearside faithful thinking back to 1973 and the possibility of an unlikely repeat.

Simply reaching the last four is a huge achievement for Mick McCarthy’s men after the trauma of relegation to the Nationwide League and the blood-letting which followed, and with Millwall and Tranmere still in the hat, a kind draw tomorrow could hand them a genuine chance of a trip to the Millennium Stadium.

What is more, they thoroughly deserve their place in the semi-finals after out-playing Sheffield United in front of a crowd of 37,115, the bulk of whom left celebrating an achievement which was beyond their wildest dreams a few short months ago.

While the prize on offer this afternoon was big enough, the focus for both sides in the longer run is promotion to the Barclaycard Premiership.

If that is to happen, it will more likely than not involve the drama of the end of season play-offs and another day in Cardiff, although on the evidence of this showing at the Stadium of Light, one of the combatants will be better equipped than the other for the rigors of top flight football.

Sunderland, despite the cull which left McCarthy desperately trying to knit together a team of misfits he could not offload, youngsters and free transfers, were far superior before the break as they tore into the Blades and left them battling to keep their heads above water, and kept their heads after it despite a fightback.

With Jason McAteer and Jeff Whitley providing the fulcrum in central midfield, wide men Julio Arca and John Oster, assisted by overlapping full-backs George McCartney and Stephen Wright, were able to run at their markers with a regularity to leave Phil Jagielka and Robert Kozluk under intense pressure.

Target man Kevin Kyle, again the willing workhorse, was more than a handful for Robert Page and Chris Morgan, and that allowed Smith to drop off and work the width of the pitch.

By contrast, United, who lost lone striker Ashley Ward through injury with just nine minutes gone, made little impression on Phil Babb and Gary Breen, with substitute Wayne Allison getting little support from Michael Tonge and Andy Parkinson and only marginally more from Peter Ndlovu.

Smith had already headed an Oster cross straight at goalkeeper Paddy Kenny when he fired his side in front by rounding off a flowing 15th-minute move.

McCartney accepted Mart Poom’s throw out and exchanged passes with Arca before picking out the striker on the edge of the penalty area.

He took one controlling touch before thumping a left-foot shot across Kenny and into the back of the net, and the pattern for the first half was set.

Chances, however, were few and far between as the Black Cats continued to dominate, although McAteer sent a looping header just wide four minutes before the break.

For their part, the Yorkshiremen created only two openings of note, both falling to Tonge, who drilled an eighth-minute free-kick narrowly off target and then fired wastefully over 13 minutes before the break.

Neil Warnock knew he had to change it at half-time and sent on Paul Peschisolido and Alan Wright for Parkinson and veteran midfielder Stuart McCall, and his troops responded quickly.

Morgan got his head to a Tonge corner and Jagielka just failed to connect in front of goal on 48 minutes, and then Allison saw a shot blocked by Breen and Ndlovu missed his kick in front of goal after Allison had headed down a Wright cross.

The travelling fans sensed a resurgence, but it might have been killed in its infancy on 56 minutes when Smith span away from Page and fed Oster before heading into the box to collect his cross on his chest, only for Morgan to intervene.

Sunderland, having been rock solid in the first half, looked decidedly unconvincing at the back, but as the storm abated, they regained their composure.

Ndlovu skied a shot on the turn high over on 66 minutes, but as United poured forward, they left gaps at the back which the home side, with a little more precision, could have exploited.

McCarthy’s men were dealt a blow with 15 minutes remaining when Arca was stretchered off, and they were appealing in vain for a penalty three minutes later after Kyle went down under Morgan’s challenge, but referee Steve Dunn waved play on.

However, they saw out the remaining minutes – including more than six for stoppages – with some comfort to complete an excellent afternoon’s work.