The Blades recorded a first win at Carlisle's Brunton Park since 1980 and in the process put further presure on the League One leaders.
First half goals from Ryan Flynn and Nick Blackman put the Blades in control before a Carlisle revival saw Danny Livesey pull a goal back for the home side.
However, late on a goal was credited to Neill Collins as he blasted home after Michael Doyle had challenged with goalkeeper Adam Collin from a Blackman corner to secure the points.
There were five changes from the midweek Johnstone's Paint Trophy exit with Porter, Blackman, McDonald, Miller and Collins all starting. It meant McAllister, Cofie, McFadzean and Williams all dropped to the bench and there is no place for Cresswell. Carlisle's team included three former Blades in McGovern, Cadamarteri and Thirlwell, who captained the home side.
Blackman again began on the right and was involved early on, helping win the game's first corner and providing a long throw from which Collins showed his aerial prowess in the home side's box. Miller also produced a neat turn in the opening minutes but he was unable to get a shot away to test Collin.
Carlisle's attempts in the first 15 minutes saw Collins block from Garner and Long gather a shot from distance by Noble at the second attempt following a bobble before the Blades went back on the offensive.
A McDonald effort was parried by goalkeeper Collin and from the rebound Blackman's powerful sidefooter with his favoured left boot was blocked but the opening goal was just a matter of seconds away. Blackman's low inswinger from the right had pace and FLYNN drifted in unmarked at the back post to slot home from a matter of yards.
Cadamarteri had a shot saved by Long after Garner refused a shooting opportunity, whilst the home outfit's Cadamarteri and Noble both picked up bookings for fouls. A block denied Flynn a second as he hammered toward goal but the goalscorer was involved as the Blades doubled the lead on 34 minutes.
BLACKMAN was involved in a neat move down the right flank at least three times, linking up with Westlake and Flynn, before the leading scorer slotted between the home goalkeeper's legs from an acute angle.
Miller was the first Blade to be booked, for a challenge on Robson, but the impetus continued and a measured Hill shot was deflected wide, whilst McDonald's drilled effort from the edge of the box was parried away by Collin.
The second half began with Symington being introduced and he quickly scuffed a free-kick in a dangerous position, whilst moments later McDonald, who took a couple of heavy blows in the first period, limped off and was replaced by McAllister.
A couple of Blackman crosses, with his right foot, caused problems for the home defence and at the other end the home side struck the woodwork twice in a matter of minutes just after the hour mark. Firstly, Noble half-volleyed against the crossbar after Long had punched out a free-kick and then Symington smashed against the base of a post.
The pressure from Carlisle was building and a long-range effort from Thirlwell was parried out by Long. However, United were not so fortunate with the subsquent corner from McGovern, which LIVESEY headed into the top corner with 71 minutes gone.
Long smothered another effort from Thirlwell as Carlisle's pressure continued and that would have been in manager Wilson's thinking as he threw on Ironside's fresh legs in the final ten minutes. The home side's offensive assault, though, was ended with five minutes to go with a third Blades goal. It was from a Blackman corner, Doyle challenged with goalkeeper Collin and the ball looked to be crossing the line when COLLINS made sure.
A powerful free-kick from Symington was punched away by Long as Carlisle attempted to hit back but their spirit had been broken and the four minutes of added time only saw a Robson effort gathered by Long before the Blades could start the long journey home with the points safely in the bag.
Carlisle: Collin, Robson, McGovern, Livesey, Noble, Cadamarteri (Beck 61), Thirlwell, Edwards, Potts, Garner, Chantler (Symington 45).
Unused: Welsh, Loy, Todd, Gillespie, Gjokaj.
Blades: Long, Westlake, Maguire, Hill, Flynn, Doyle, Porter (Ironside 81), Blackman, McDonald (McAllister 48), Miller, Collins.
Unused: Cofie, McFadzean, Williams, Kennedy, Coyne.