Leigertwood was one of several players caught up in a melee at the end of the 2-2 draw at Cardiff on Tuesday night as Craig Bellamy scored an equaliser deep into stoppage time with a disputed free-kick.
The on-loan QPR man was not booked at the time but was charged with violent conduct by the FA retrospectively and begins his suspension against Rangers on Friday night.
He said: "I'm very sorry for letting people down; the fans, my team-mates and the manager.
"The game meant a lot to us and I was frustrated with the decision but there is no excuse.
"I reacted badly and now I have to live with it."
Source: PA
Source: PA