After an impressive end to 2015, United could not kick-off 2016 with a victory.
Despite an impressive display, United were hit by three impressive Peterborough goals. Billy Sharp netted his fourth in as many games but it wasn't enough for three home points.
Boss Adkins was forced into a change to his starting line-up for the first game of 2016. Sammon took over from Done, who failed to recover from the injury he sustained against Bradford City. On the bench, Adams returned after his three-match suspension.
A couple of early corners and a spell of pressure indicated that United made a bright start. The Posh appeared to panic in defensive situations but they weathered the storm and Sharp shot over from a similar position from which he scored five days earlier.
The impressive start, however, was blighted when Peterborough netted with their first attack; on 18 minutes WASHINGTON surprised everyone with quick, powerful shot which rocketed into the Kop goal.
The visitors went close to a second soon after when Hammond was dispossessed but a combination of Long and Edgar kept out Washington and Taylor.
From then, for the remainder of the half, it was one-way traffic as United pushed the Posh back. Sammon was denied a penalty after being brought down by Baldwin, Basham half-volleyed into Alnwick's arms and Sharp struck a post.
The chances continued. Excellent work from Woolford saw a Coutts effort blocked and Alnwick clawed away an Edgar header from a Coutts corner but the leveller was moments away. The industrious Sharp was heading away from goal when he was fouled by Smith and referee Bond pointed to the spot. Despite a couple of misses, SHARP took responsibility and drilled home.
United remained on the front foot, with Peterborough picking up a couple of bookings in the process of stopping the home side. Following a Santos foul on Basham, a Coutts free-kick was on target but pushed away by Alnwick and close to half-time Basham headed wide a Woolford free-kick.
The Blades could not replicate the impressive start to the second half and were punished. Forrester had already tried his luck before, on 48 minutes, OZTUMER took advantage of Basham backing off before hitting an impressive 25-yard effort beyond Long and into the top corner.
Maddison fired wide for Peterborough following a patient move and Baxter was introduced as boss Adkins searched for fresh impetus and he had a shot blocked soon after.
Long saved from Maddison as Peterborough looked dangerous on the break but United were trying to force the play. Adams was introduced with 20 minutes to go, whilst Sharp attempted an acrobatic effort from a Coutts cross but Alnwick saved.
For most of the second half, Peterborough, expectedly, slowed the action at every opportunity. It looked like the tactic had been punished when United levelled on 83 minutes. A move involving Coutts, Brayford and Adams saw Woolford deliver a cross and although Basham's effort looked to be missing the target, the ball hit the head of the horizontal BALDWIN and trickled over the line.
However, Peterborough hit straight back and although there will be questions of the defending, the away fans were celebrating an impressive goal. Substitute SAMUELSEN danced through at least four Blades shirts before calmly beating Long.
Six minutes of added time was announced, due to Peterborough's slowing tactics, Oztumer blocked from Baxter and Brayford fired over from the resulting corner. Peterborough also blocked from Adams after Collins, an auxiliary striker, laid off, before the final whistle signalled defeat.
Blades: Long, Brayford, Basham, Coutts, Sharp, Collins, Woolford, Sammon (Baxter 56), McEveley (Adams 71), Edgar, Hammond.
Unused: Howard, Flynn, Campbell-Ryce, Reed, K Wallace.
Peterborough: Alnwick, Smith, Baldwin, Taylor, Oztumer, Maddison (Samuelsen 78), Almeida Santos, Washington, Beautyman, Fox (Wilson 45), Forrester (Addison 90).
Unused: Angol, Henry, Coulibaly, Nicholson.