Leeds United were made to pay for wasted chances in the first half as two long-range goals from Shaquile Coulthirst inflicted their first pre-season defeat at London Road.
Peterborough United came through a 45-minute onslaught from Leeds to respond to an early Alex Mowatt finish and snatch victory through Coulthirst’s second-half efforts.
Mowatt’s early volley was the result of impressive pressure from Leeds and Garry Monk’s side created numerous opportunity before half-time.
But their failure to take any others saw Peterborough recover and claim victory as United - with numerous players making their first 90-minute appearances of the summer - ran out of steam in high temperatures.
Monk fielded a far stronger side than he had at Guiseley last night and Leeds got on top of Peterborough quickly, dominating the League One team and producing the aggressive, positive football which their head coach promised to deliver.
Mowatt took two minutes to draw a full-stretch parry from goalkeeper Ben Alnwick and Alnwick, a former Leeds loanee, was under constant pressure before half-time.
He was beaten by Mowatt after 16 minutes when the impressive Kemar Roofe turned right-back Michael Smith inside out and delivered a cross which Mowatt volleyed him at close range. Back in a more central position, the midfielder saw more chances in a single game than he saw in several last season.
Antonsson and Roofe both went close and Mowatt missed by inches from 20 yards before Hadi Sacko drew an impressive save from Alnwick after sprinting into space towards the end of the half.
Peterborough struggled to compete in oppressive heat but a couple of defensive mix-ups involving Sol Bamba and goalkeeper Rob Green almost gifted them an equaliser. Shaquile Coulthirst saw a scuffed shot cleared off the line on 36 minutes after Green failed to claim a hanging cross.
Peterborough, however, made the most of the break and levelled on 50 minutes with a brilliant finish from Coulthirst.
The forward pounced on a weak clearing header from Kyle Bartley and beat Green with a volley which found the keeper’s bottom corner.
United’s display lost its sting rapidly and Peterborough began to threaten regularly until Coulthirst struck again with another fine effort on 65 minutes. Left unattended 25 yards from goal, his low effort flew into the opposite corner of Green’s net.
Sacko could twice have snatched an equaliser on the break but Alnwick denied him on both occasions by getting his body in front of the ball.
Peterborough United: Alnwick, Smith, Hughes, Tafazolli, Baldwin, Forrester, J Anderson (Edwards 63), Da Silva Lopes (Chettle 77), Maddison, P Taylor, Coulthirst. Subs (not used): Tyler, Bostwick, Nichols, Nabi, Chettle, Stevens, Freestone, White.
Leeds United: Green, Purver, Bartley, Bamba, Taylor, Murphy, Grimes; Sacko, Mowatt, Roofe (J McKay 63), Antonsson. Subs (not used): Huffer, M Taylor, Shackleton.