United's Carling Cup hopes for another season went up in smoke at the first round stage.
Port Vale - beaten 3-1 by the Blades at the same stage of the competition last year - produced the giant-killing act, thanks to two goals from Marc Richards.
His second, which proved to be the winner, was the result of a howler from goalkeeper Ian Bennett, who dropped a seemingly standard free-kick into his own net.
Wingers Little and Reid were handed debuts as boss Blackwell rung the changes for the first round tie with Port Vale. The United chief made a total of five alterations from the Championship opener with Bennett, Bromby and Sharp also recalled. On the bench, local youngsters Robertson and Roe were amongst the substitutes but only six of the seven berths were filled on the bench.
Kilgallon was handed the captaincy, in the absence of his defensive partner, Morgan, and United were quickly on the offensive, forcing Vale back. Goalkeeper Martin was forced to tip Sharp's half-volley around the post on six minutes and then Little drilled an effort just a yard wide after Howard, Sharp and Henderson had linked up. On 16 minutes Reid's attempted cross looked goalbound after a wicked deflection but the agility of Martin managed to keep the ball out.
All that Vale could manage early on was Rob Taylor causing problems for Bromby but the away side grabbed the lead with their first serious attacking move on 20 minutes. Rob Taylor's cross from the left was headed back across goal by Loft and RICHARDS found himself in a great position to beat Bennett from close range.
United did not panic and were quickly back on the front foot. The home side dominated possession and it took just 13 minutes to level the scores. Short passes from Quinn and Little resulted in SHARP picking up the ball in the box, with his back to goal, but after a neat turn, he fired beyond Martin's left hand, into the top corner.
The remainder of the first half was also United-dominated but the Vale defence protected Martin in the closing stages, although the goalkeeper did get a pat on the back from his manager, Blades-fan Adams, at the interval.
McCombe was forced to head over his own crossbar early in the second half as United continued with the good work of the first half. Martin parried a Little cross as Sharp looked ready to pounce.
On 55 minutes Reid escaped his marker on the left and delivered a cross for Henderson, who looked poised to bundle the ball over the line until Owen cleared off the line. It was Henderson's last act as he was replaced by Robertson a moment later.
Bromby headed wide Little's cross but on another rare Vale attack the visitors took the lead once more. A weak free-kick for a foul on Griffith saw RICHARDS step up and beat the wall but even he was surprised when he watched the ball slip through the hands of Bennett and into the net.
United's experienced goalkeeper saved an Owen header soon after, whilst United were quickly back on the attack. Howard's 25-yard shot, on 66 minutes, was diverted over by the merest of touches from Martin, who then kept out an effort from Robertson from the resulting corner.
Richards came close to claiming a hat-trick on 76 minutes but his header from a corner was smothered by Bennett, who, soon after, dropped another cross - McCombe almost took advantage.
Late on, substitute Treacy tries his luck from long-range and then a Sharp effort was deflected on to the top of the crossbar by the impressive Martin.
Three minutes of additional time was announced to give United an opportunity to save their cup dreams but the moments passed without another chance, although Bromby hurled in one of his long-throws and two Treacy corners were cleared.
Blades: Bennett, France, Kilgallon, Henderson (Robertson 56), Reid, Taylor, Howard, Bromby, Sharp, Little (Treacy 68), Quinn (Montgomery 81).
Unused: Morgan, Haber, Roe.
Port Vale: Martin, Stockley, R. Taylor (Horsfield 80), Griffith, McCombe, Loft, Richards, Fraser, Collins, Owen, K. Taylor.
Unused: Yates, Dodds, Lloyd-Weston, Morsy.
