Match ends, Peterborough United 1, Sheffield United 2.
Ben Davies' superb goal secured Sheffield United's first points of the season and ended Peterborough United's perfect start to the campaign.
Posh dominated the first half possession but found themselves behind when Jose Baxter applied a smart finish to a one-two with Marc McNulty.
Shaun Brisley headed in Jon Taylor's corner to level for the home side.
Taylor and Tyrone Barnett had chances to put Posh in front but Davies struck from the edge of the area to win it.
Kyle Vassell could have snatched a last-gasp point for Darren Ferguson's men but his shot was smothered by the Blades defence.
Peterborough United boss Darren Ferguson told BBC Radio Cambridgeshire:
"It's frustrating to say the least. In the first half I thought we were outstanding. Our pace and tempo, they couldn't live with it. Some of our football was outstanding.
"In that half we should have been out of sight and we switched off for one moment.
"We had two great chances in the second half through Taylor and Barnett and if we had gone ahead we would have been hard to stop."
- 22Almeida SantosSubstituted forBurgessat 62'minutes
- 3NtlheSubstituted forFerdinandat 75'minutes
- 7TaylorSubstituted forBarnettat 70'minutes
- 11BaxterSubstituted forFlynnat 83'minutes
- 12McNultySubstituted forHigdonat 71'minutes
- Scott Duncan
- Shots on Target
Second Half ends, Peterborough United 1, Sheffield United 2.
Hand ball by Kyle Vassell (Peterborough United).
Jamie Murphy (Sheffield United) wins a free kick on the left wing.
Foul by Jack Payne (Peterborough United).
Ryan Flynn (Sheffield United) wins a free kick on the right wing.
Foul by Nathaniel Mendez-Laing (Peterborough United).
Foul by Ryan Flynn (Sheffield United).
Christian Burgess (Peterborough United) wins a free kick on the left wing.
Goal! Peterborough United 1, Sheffield United 2. Ben Davies (Sheffield United) right footed shot from outside the box to the bottom right corner.
Substitution, Sheffield United. Ryan Flynn replaces Jose Baxter.
Attempt missed. Jack Payne (Peterborough United) right footed shot from outside the box is just a bit too high.
Christian Burgess (Peterborough United) wins a free kick in the attacking half.
Foul by Chris Basham (Sheffield United).
Corner, Sheffield United. Conceded by Sean Brisley.
Substitution, Peterborough United. Kane Ferdinand replaces Kgosi Ntlhe because of an injury.
Attempt missed. Tyrone Barnett (Peterborough United) right footed shot from the right side of the six yard box is close, but misses to the left.
Substitution, Sheffield United. Michael Higdon replaces Marc McNulty.
Substitution, Peterborough United. Tyrone Barnett replaces Jon Taylor.
Kgosi Ntlhe (Peterborough United) wins a free kick in the attacking half.