Lloyd Jones reflected on Saturday afternoon's defeat to Millwall.
The Addicks were beaten 4-0 at The Den.
"We were not good enough. We have let the fans down and we have let ourselves down," Jones said.
"We lost too many duels everywhere. No one individually can say they came out on top today, it's been disappointing."
"The goals we conceded were disappointing, soft, uncharacteristic of us, especially in the early parts of the season. But at the moment we need to be together, we need to fight more," he added.
"We have to regroup as a team. No one is going to feel sorry for us, this is the Championship. We still have a long way to go, a lot of games to play. So we have to regroup, work hard, get our heads down and get ready for another big game next on Saturday."
The Addicks are back in action on Saturday, January 31st, as they take on Leicester City at the King Power Stadium (KO 12.30pm GMT).
