United's hopes of reaching the Capital One Cup final remain very much alive following a determined performance at White Hart Lane on Wednesday night.
The visitors more than matched their Premier League opponents for more than 70 minutes, before Andros Townsend settled the first-leg with a penalty kick following a handball by Jay McEveley.
But backed by 4,000 fans in the capital, United now head back to Bramall Lane still with realistic hopes of overturning the deficit and securing a place in a Wembley final.
Nigel Clough made three changes for the semi-final clash in North London, with Basham, Flynn and Reed replacing Kennedy, Alcock and Baxter, who all dropped to the bench. For the home side, former United Academy graduate Kyle Walker started, with Emmanuel Adebayor captaining Spurs.
The game started at a frantic pace and it was United doing most of the attacking, from the kick-off Murphy put Spurs on the back foot and won a free-kick, before Flynn almost capitalised on some indecision amongst the home defenders.
The visitors continued to look bright in possession and after Doyle had shot over, Scougall robbed Townsend in the middle of park before feeding McNulty who saw his shot at goal blocked by Vertonghen.
The first flash point of the clash came in the 16th minute, when Adebayor raised an arm into Reed's face; the striker was booked by referee Swarbrick following the incident as the game remained an even contest.
In the 22nd minute it was United who came close to opening the scoring, Scougall fed Campbell-Ryce on the right, he beat Davies and flashed an effort agonisingly wide. Spurs responded with Dier heading towards goal from a Townsend free-kick, but his effort was tipped round the post by Howard.
After another even spell, it was the home side who should have taken the lead in the 34th minute. Eriksen's pinpoint lifted through ball found Adebayor who had beaten the offside trap, but McEveley's presence was just enough to put the home skipper off and he fired high and wide.
Six minutes later it was United through Scougall that came within inches of shocking the hosts. The Scottish midfielder disposed Davies and after combining well with Reed he shot just wide from the edge of the penalty area with Vorm seemingly beaten.
The last action of the first-half saw Dier head wide from another Townsend free-kick on the right, although Howard appeared to have his angles covered.
United began the second-half with a counter attack that led to Doyle firing over following corner, before the offside brought Townsend's progress to an end with the England international in the clear from Eriksen's pass.
McEveley went into the book in the 54th minute for a foul on Townsend on the edge of the penalty area, but the resulting free-kick came to nothing.
Following a spell with little to report, United had a scare in the 69th minute. Following a short corner between Eriksen and Kane the resulting ball into the box caused McEveley and Harris a problem or two before Swarbrick spotted a foul to release the pressure.
The home side's growing pressure did eventually lead to the first goal of the game in the 74th minute. Vertonghen's ball into the penalty area was expertly controlled by Soldado and as the ball bounced up it caught the hand of McEveley and the assistant referee waved to indicate a spot-kick which was duly dispatched by TOWNSEND, despite Howard diving the right way.
At the other end, McEveley tried to atone for giving away the penalty, but his header from Scougall's free-kick looped wide of the far post. Clough then made his first change with Baxter replacing McNulty up front.
As the game entered the final five minutes, a marauding run from Campbell-Ryce won a corner and lifted the spirits of the travelling United contingent, then moments later Baxter just failed to connect with a right-wing crosses on two separate occasions.
Three minutes of added time were indicated and it was the Blades who finished the strongest. Baxter ran down the left-wing and from his cutback Murphy curled an effort just wide to end a terrific battling performance from the Blades which was acknowledged by the vocal travelling supporters.
Spurs: Vorm, Walker, Dier, Vertonghen, Davies, Townsend, Mason (Dembele 64), Stambouli (Paulinho 74), Eriksen, Adebayor (Soldado 64), Kane.
Unused: Friedel, Kaboul, Rose, Lennon.
Blades: Howard, Harris, Basham, Flynn, Doyle, Murphy, Scougall (K. Wallace 87), McNulty (Baxter 82), McEveley, Campbell-Ryce, Reed.
Unused: Alcock, Higdon, Turner, Kennedy, Adams.