Millwall were defeated 2-1 by Peterborough United in the Sky Bet Championship on Saturday afternoon.
Tom Bradshaw's fifth goal in seven matches came in the 16th minute, but Jonson Clarke-Harris stepped off the bench to win the game with a double in four minutes for the hosts.
Gary Rowett opted to keep the same XI and substitutes bench from last Saturday's 3-1 victory over Birmingham City, meaning the likes of Danny McNamara, Tom Bradshaw and George Evans kept their starting berths.
The first opportunity came as early as the second minute and went the way of the hosts, but Jack Taylor sent an effort over the crossbar.
Harrison Burrows and Sammie Szmodics then combined to test Bartosz Bialkowski in the early going, before The Lions' first attempt saw Evans balloon an effort well over.
Dan Butler had to withdraw through injury with just 11 minutes on the clock, with Millwall taking the lead five minutes later as Jed Wallace controlled Scott Malone's pass and crossed for Bradshaw, who struck home to open the scoring.
From there, however, Peterborough looked the more likely to register on the scoresheet, with Szmodics at the apex of every attack, but a combination of Bialkowski and a stoic Millwall defence kept the sheet clean. At the other end, The Lions were attempting to muster chances to score a second, but could only find the grasp of goalkeeper Dai Cornell from Bradshaw's header.
Bialkowski had to tip over from Jorge Grant as the second-half got underway, but it was the introduction of Clarke-Harris which tipped the game in Peterborough's balance. After arriving onto the field in the 56th minute, the attacker then went on to score a quick-fire double - in four minutes - to turn the game on its head and give The Posh all three points.
First, the striker bundled the ball home to equalise on 64 minutes, before he was in the right place at the right time to tap home the winner with 68 minutes on the clock.
Dai Cornell had to keep out Bradshaw's effort as The Lions looked for a way back into the game, but despite a treble substitution of Mason Bennett, Matt Smith and Sheyi Ojo, Millwall could not find an equaliser, slipping to defeat at the Weston Homes Stadium.
Peterborough United: Cornell, Edwards, Butler (Tomlinson 11'), Thompson, Szmodics, Taylor (Coventry 87'), Dembele, Grant, Knight, Burrows, Norburn. Subs not used: Blackmore, Kent, Clarke-Harris, Poku, Corbett.
Booking: Norburn, Cornell
Millwall: Bialkowski, McNamara, M. Wallace, Hutchinson, Cooper, J. Wallace (Bennett 74'), Bradshaw, Malone (Ojo 74'), Afobe (Smith 74'), B. Mitchell, Evans. Subs not used: Long, Kieftenbeld, Pearce, Saville.
Scorer: Bradshaw 16'
Booking: Malone, McNamara, Hutchinson, B. Mitchell, Evans
Referee: Mr L Doughty
Attendance: 9,140 (2,356)