Addicks boss Chris Powell was given his first coaching role by Pearson, but he duly completed a Championship double over his former club following Charlton's 2-1 win at The Valley back in August.
Yet Powell was not the only former Leicester man to make an impact on the night as Yann Kermorgant returned to haunt his previous employers - scoring the first then setting up Danny Haynes for a spectacular 20-yard winner after Chris Wood had equalised.
"It's a disappointing result," said Pearson. "I think they came to do a bit of a job on us and they did it well in terms of getting everybody behind the ball and limiting our ability to play the type of football that we do.
"When you concede the types of goals that were conceding it gives us a problem in terms of winning games and that's really the top and bottom of it.
"I don't think we deserved to lose the game but we have. I know the second goal is a good strike but we've not dealt with a situation I'd expect us to snuff out. From a defensive point of view it's certainly avoidable."