Charlton 0 Walsall 1
Charlton missed out on going second after a poor performance on Sunday saw them lose at home to Walsall.
The midland side, who started the match bottom of League One, took all three points thanks to a Matt Richards goal in the second half.
The result came as a shock to the fans and ended the Addicks 11 match unbeaten run.
After the game, manager Phil Parkinson said he was at a loss to explain what caused the defeat.
"It was a terrible performance from us; I can't hide away from it," he said. "It's a performance I'm finding difficult to explain.
"It wasn't three or four players who had an off day, everyone did. You can't say anybody played well. When that happens, there's normally an underlying reason. What that reason is, we'll have to sit down and search for it."
The Addicks boss said sorry to the fans after the result, which was Charlton's second home defeat of the season.
"This is a team which has had a terrific run," he said. "They're an honest group of lads and we've got to pick ourselves up and go again.
"That was almost the same Charlton team which won 5-1 at Peterborough United. But that's football for you, it's not an exact science.
"Apologies to our supporters because it was a poor performance. We haven't given them too many of those in recent weeks, but today was not a good one."
Walsall enjoyed the lionshare of possession and made the most chances in an intriguing encounter at The Valley.