"We got turned over today and it is hugely disappointing," the Addicks boss said.
"It was a poor performance and we were second best throughout. Leicester weren't fazed by coming to play us and thoroughly deserved to win.
"I don't know why we were so bad. They outfought us physically and we were lacking in design. Let's hope it's a one-off.
"The FA Cup is very much what happens on the day but you have to earn the right to progress and we just didn't do that today.
"The expectancy levels are such that Premiership sides are always expected to win this kind of game but it just never happened for us.
"I hope they get a good draw because they deserve it."