United's string of six clean sheets and seven matches unbeaten was unceremoniously ended at Stevenage on Saturday.
A Dani Lopez hat-trick was the catalyst for Stevenage's win and leaves the Blades without a victory at the Lamex Stadium in three visits.
Danny Wilson named an unchanged team for the visit to Stevenage but did recall Porter to the bench at the expense of Ironside.
The home side made a concerted effort from the kick-off, backed by their fans, and an early shot from Lopez was deflected wide after Robson had been dispossessed. There was a further issue for the Blades to deal with on ten minutes when Murphy limped off after treatment and was replaced by McFadzean.
In the early stages the Blades struggled to find a rhythm and took 18 minutes to register a chance, McDonald well off target with a first time effort after Kitson laid off Flynn's cross. McDonald, however, did better in his provider capacity soon after, threading a pass to put Flynn in the clear but the winger's shot was turned around the post by goalkeeper Arnold.
A couple more opportunities fell to United in the following minutes around the half hour mark, but Robson's header from McMahon's cross was at Arnold and Kitson's first touch let him down when Doyle found him with a forward pass.
Stevenage also had chances. Long saved from Grant, unknowing the striker was offside and Haber was slipping as he attempted to turn home a Akins cross. The home side, however, did snatch the lead as half-time approached. LOPEZ managed to get through Collins on the right before poking beyond Long at the near post.
It could have been even worse for United as there was still time for another effort. Buoyed by his goal, Lopez tried his luck from 25 yards and his shot was dipping in before Long used all his inches to tip over the crossbar.
United made a second change at the break, Forte taking over from Flynn, whilst a run from McFadzean livened the Blades fans and put the home side under pressure - it proved to be a false dawn as Stevenage doubled their lead on 50 minutes. A half-cleared corner was chipped back into the penalty area by Mahon and as the visiting players looked towards the linesman, LOPEZ stole in and beat Long with a controlled volley.
Robson, now operating from the right, almost got on the end of a Forte poke forward and from the resulting corner, Arnold touched over a Maguire header. The Blades went closer still on 53 minutes from a McMahon cross but McFadzean's looping header hit the underside of the crossbar and a defender on the line before being cleared.
Lopez had a hat-trick chance, which flew wide before he completed his treble on 64 minutes. There was a spell of unpleasantness with the referee speaking to both captains before Stevenage turned defence into attack, the ball being shifted to the right for LOPEZ to smash home his third from the edge of the box.
It got worse for the Blades as Stevenage quickly added a fourth. This time AKINS was allowed space to cut in from the right and although Long got a hand to the shot, the goalkeeper was unable to stop the ball trickling into the corner of the net.
Robson was booked for lunging in on Dunne as the Blades looked frustrated late on. Long was forced to save from Grant and to prove it was not United's day, a two-on-one situation failed to bring a consolation, Arnold saving from Kitson after Forte laid off.
Referee Russell waved away United's penalty appeals when McFadzean went down under a Comminges challenge which summed up the visiting side's luck and the three minutes of added time was not going to crucial as the Stevenage victory was already sewn up.
Stevenage: Arnold, Hills, Grant, Dunne, Haber (Beleck 75), Akins (Hoskins 86), Roberts, Mahon, Comminges, Lopez (Tansey 80), N'Gala.
Unused: Day, Freeman, Iro, Shroot.
Blades: Long, Maguire, Hill, Flynn (Forte 45), Doyle, McDonald, Kitson, Collins, Robson, Murphy (McFadzean 10), McMahon.
Unused: Westlake, Higginbotham, Porter, Poleon, Coyne.