A late goal from Ben Davies earned Sheffield United all three points following a pulsating Sky Bet League One encounter at London Road, but Peterborough United can count themselves extremely unlucky not to take at least a point for a spirited effort against all the odds.
Posh were forced into three enforced changes because of injury and struck the woodwork twice against the Blades in front of over 6,500 fans.
Posh flew out of the traps, playing at an excellent pace in the opening moments and forced goalkeeper Mark Howard into the first save of the evening, making a routine stop to deny Conor Washington's low drive.
On 10 minutes, Washington found himself in behind the back line following a powerful Payne header, but the ball wouldn't sit down for the striker, bouncing high making his effort hard to control with the volley going over as a result.
Former Posh defender Craig Alcock fired wide from distance on the quarter hour mark. At the other end, Taylor struck the outside of the post as he tried to squeeze in a shot from a tight angle after Ntlhe's cross was only half cleared.
Taylor fired over on 17 minutes after Vassell had been tackled inside the penalty area. The deadlock was broken on 25 minutes and it was superbly worked by the visitors, incisive one-twos around the box and the ball was worked to BAXTER who fired across Alnwick and into the back of the net.
Teenager Jermaine Anderson fired wide with his left-foot after a glorious drag back with his right-foot on 29 minutes as Posh tried to respond to the blow of losing a goal.
On 34 minutes, Posh deservedly levelled the scores and it came from an unlikely source. A corner from the left by Jon Taylor was met powerfully at the near post by Shaun BRISLEY for his first goal since netting in the Johnstone's Paint Trophy final at Wembley.
Payne fired over from 30-yards moments later as Posh, backed by a noisy home crowd, pressed for a second goal. On 43 minutes, Vassell was denied by Howard, the goalkeeper doing well to smother the toe-poke at the feet of the former Bishop's Stortford man.
Baxter fired over moments after the re-start after getting across the front man at the near post. At the other end, Vassell fired wide of the near post after a clearance rolled his way after good work from Mendez-Laing in the build-up.
Baxter fired wide of the near post after good work from Davies down the left as Santos slipped at a crucial time. On 53 minutes, Posh created a superb opportunity to take the lead as Mendez-Laing cut the ball back well for Taylor, but his goalbound shot appeared to strike Vassell before going wide.
Mendez-Laing tested Howard with a curler from the edge of the box, which the keeper grabbed at the second attempt. Santos produced a stunning last ditch tackle to stop Baxter from scoring just after the hour mark, a wonderful piece of timing from the centre back.
It was the last action for Santos who was replaced by Christian Burgess who joined from Middlesbrough earlier in the day. The Blades had the ball in the back of the net on 64 minutes, but the offside flag was raised to chalk the effort off.
Ntlhe tricked his way past an opponent moments later, but his shot from range was ambitious and went well wide of the target. Tyrone Barnett replaced the tiring Taylor on 70 minutes.
Barnett nearly scored with his first touch, spinning round the back to meet a Mendez-Laing free-kick only to divert his shot wide of the far post. Posh lost the services of Kgosi Ntlhe on 75 minutes with Kane Ferdinand coming on in his place.
On 85 minutes, the Blades re-took the lead as a throw in from the left was only half cleared and Ben DAVIES lashed the ball home past a rooted Alnwick, who had no chance of keeping the cleanly struck effort out.
Final Score: Posh 1-2 Sheffield United
Posh: Alnwick, Smith, Ntlhe (sub Ferdinand 75min), Brisley, Taylor (sub Barnett 70min), Payne, Vassell, Washington, Anderson, Mendez-Laing, Santos (sub Burgess 63min). Unused subs: Day, McCann, Newell, H. Anderson.
Sheffield United: Howard, Alcock, Basham, Doyle, Murphy, Baxter (sub Flynn 84min), Collins, McNulty (sub Higdon 71min), Davies, McGahey, McEveley. Unused subs: Turner, Harris, Flynn, Campbell-Ryce, Reed.
Attendance: 6,578 (1,062 Sheffield United fans)