The Blades suffered an opening day defeat for the first time since 2008 as the Sky Bet League One campaign kicked off on Saturday.
A debut goal from Michael Higdon was a positive, as were a number performances, but goals from Aaron Wilbraham and old foe Wade Elliott gave Bristol City the victory.
Louis Reed made his first senior start, one of two teenagers to play 90 minutes for the Blades.
When the team sheets were handed in an hour before kick-off there were a few surprises. New boy Higdon started...and was handed the captain's armband! Teenagers McGahey and Reed were also members of the starting XI, whilst senior professionals Doyle and Collins were on the bench. In total, four of the new signings started and two more were on the bench.
The Sky Sports cameras saw an energetic start from both sides but the visitors were on the offensive first - from Freeman's free-kick, Smith fired over. Higdon's first contribution was to charge down a clearance from Fielding and then the big striker laid off for Flynn to shoot at the goalkeeper.
A shot from Harris curled wide as United looked to be getting on top before City struck the first blow on 20 minutes. Basham lost possession to Freeman in midfield and following Little's run down the right, WILBRAHAM's back post header found the target, despite Howard getting a hand to the ball.
United - and the home crowd - responded positively. From a Harris cross, Higdon challenged Fielding and from the resulting loose ball Scougall's goalbound effort was blocked by Ayling and the big striker then saw a header from a Davies cross tipped over by the visiting goalkeeper.
City were thankful for another defensive clearance on 29 minutes, Flint doing the honours after Flynn and Murphy caused problems, but the pressure was mounting and the equaliser duly arrived within minutes. Davies delivered a free-kick from the right and in a crowded penalty area HIGDON nodded past Fielding.
The Blades looked to use the momentum and went on the search for the lead. From Flynn's cross Scougall rose highest but headed over and then Basham volleyed wide with Higdon and Scougall again involved.
City stemmed the flow of United's attacks and a long-range Freeman shot was saved, whilst late in the half the major talking point was a collision between Little and Harris which left the Blades defender needing lengthy treatment before he was able to continue.
The first incident in the second half involved the referee, who booked Murphy for diving, despite him being clipped as he chased the ball. Like the first half, City began brighter - Wilbraham kicked the ball against himself following a pull-back by Baldock, who then shot at Howard moments later.
Former City player Campbell-Ryce was introduced for his debut just after the hour, taking over from Flynn, but with the next meaningful attack the visitors regained the lead. On 72 minutes, a long, crossfield ball was headed down by Little, Wilbraham's flick found the run of ELLIOTT, who smashed past Howard from 12 yards.
Freeman almost added a third when he danced through three red and white shirts but fired wide and soon after McNulty was introduced for his debut, joining Higdon in attack.
Davies powered into the box and after hitting the deck became the second Blade to be booked for diving, whilst City were saved by a third defensive clearance on 80 minutes. Campbell-Ryce's shot was deflected to Murphy, whose shot struck the arm of goalkeeper Fielding and a post before Flint cleared off the line.
Higdon almost got on the end of a Harris cross and United's last throw of the dice was Baxter taking over from Basham. Predictably, the Blades had most of the possession late on and five added minutes were announced at the 90-minute mark. But the home side were unable to force a second leveller in the injury-time period and suffered defeat.
Blades: Howard, Alcock, Harris, Basham (Baxter 86), Flynn (Campbell-Ryce 64), Murphy, Scougall (McNulty 76), Davies, McGahey, Higdon, Reed.
Unused: Doyle, Willis, Collins, Porter.
Bristol City: Fielding, Little, Williams, Flint, Smith, Elliott (Wagstaff 89), Baldock (Emmanuel-Thomas 90), Freeman (Pack 76), Cunningham, Wilbraham, Ayling.
Unused: El-Abd, Richards, Burns, Bryan.