The Addicks slumped to a 4-1 defeat at Peterborough on Saturday afternoon.
Andrew Hughes, Marcus Maddison (pen) and Jack Marriott (2) were the Posh scorers, with Michal Zyro getting Charlton’s goal.
Naby Sarr, Johnnie Jackson and Tariqe Fosu came into the team, replacing Jay Dasilva, Ahmed Kashi and Mark Marshall.
Karl Robinson switched to a 4-3-3 shape, with Sullay Kaikai and Fosu pushing in to support Josh Magennis.
The game was an open affair, with both sides having chances, but the pivotal moment of the game came early in the second half.
Magennis, Fosu, Jake Forster-Caskey and Kaikai all had chances in the opening period. Chris Forrester, Omar Bogle – who hit the post – and Marcus Maddison all had opportunities for Peterborough.
But it was Posh who snatched the lead a minute before the interval. The Addicks failed to clear a Maddison free-kick properly, and when the ball was recycled, Hughes was on hand at the far post to touch it home.
Charlton had a glorious opportunity to restore parity ten minutes into the second half. Magennis was pushed in the back in the area, and stepped up to take the penalty himself.
He sent Jonathan Bond the wrong way, but his shot whistled wide of the post.
Four minutes later Posh were also awarded a penalty when Sarr brought Maddison down. The winger converted the spot-kick to double the hosts’ advantage.
Shortly after, Robinson replaced Magennis with Zyro, and the Polish international reduced the arrears after 74 minutes. His glancing header from Ben Reeves’ cross beating Bond.
Jack Marriott added two late goals. Peterborough stole the ball in midfield and played it in to Marriott, who spun and fired home after 82 minutes.
Three minutes later referee, Brett Huxtable, played a good advantage, and Marriott converted a right-wing cross.
It was a hugely disappointing result, which may have been different had Charlton had taken the opportunity to level from the penalty spot early in the second half.
Robinson had this to say after the game:
“It didn’t feel like a 4-1 scoreline. You’ve got to give them tremendous credit. The difference is they’ve scored goals.
“We don’t take our chances. It is as blatant as that. That’s been our problem all season.”
The Addicks travel to Blackpool on Tuesday and need to claw back some points on the top six.
Charlton: Amos; Solly, Konsa, Pearce, Sarr; Aribo, Jackson (Ajose, 68), Forster-Caskey; Kaikai (Reeves, 64), Magennis (Zyro 64), Fosu.
Subs (not used): Maynard-Brewer, Bauer, Marshall, Lennon.
Goal: Zyro 74.
Booked: Solly 40 (dissent), Sarr 85 (foul).
Peterborough: Bond; Shephard, Taylor, Baldwin, Hughes; Forrester, Ward (Doughty70), Da Silva Lopez (Anderson, 83), Maddison; Bogle (Lloyd, 76), Marriott.
Subs (not used): O’Malley, Morias, Freestone, Cooper.
Goals: Hughes (44), Maddison (pen, 59), Marriott (81, 84)
Booked: Baldwin 40 (foul).
Referee: Brett Huxtable (Devon).
Attn: 6,337 (883 Charlton).