Paul Warne was left to rue individual errors after his Rotherham United side crashed to defeat at Peterborough.
Keiffer Moore’s fourth goal of the campaign looked enough to earn a 1-1 draw, eight minutes after Jack Marriott’s 47th-minute opening strike.
But a slip by defender Semi Ajayi - on 75 minutes - allowed Marriott to steal in, before lobbing Millers goalkeeper Richard O’Donnell.
“The lads were obviously disappointed in there but they have to take responsibility for what they do,” Warne said.
“It was end-to-end and I thought there would be goals in the game.
“Prior to the game, I thought it would be a 3-2 or a 4-3. In the first half, it was a pretty even match although I was not best pleased with how we played in the first half. In the second, we played a lot better but a couple of individual errors massively cost us a couple of goals.”
Rotherham were caught cold at the start of the second half, Marriott firing home, via the inside of the post. But the visitors were deservedly level on 55 minutes, Moore heading in Lee Frecklington’s left-wing cross.
Twice Marriott was denied by the woodwork, after hitting the post and crossbar, while the Millers had a ‘goal’ ruled out as Jamie Proctor’s header was chalked off for offside.
Then came Ajayi’s unfortunate error, to gift Posh all three points and leave Rotherham mid-table with just three points from their opening three games.
Peterborough: Bond, Tafazolli, Baldwin, Taylor, Edwards, Grant, Doughty, Da Silva Lopes (Hughes 82), Maddison (Forrester 82), Morias (Kanu 71), Marriott. Unused substitutes: Shephard, Lloyd, O’Malley, Borg.
Rotherham: O’Donnell, Mattock, Ihiekwe, Ajayi, Emmanuel (Forde 82), Newell, Frecklington, Potter, Williams (Taylor 77), Proctor (David Ball 72), Moore. Unused substitutes: Vaulks, Purrington, Clarke-Harris, Bilboe.
Referee: R Joyce (Cleveland).