Charlton are bracing themselves for the big one as both coach Mark Kinsella and defender Frazer Richardson called for cool heads.
Kinsella warns of Millwall ahead of Saturday's visit to The Den: "They're a big, strong physical side.
"We're expecting a tough game with a big atmosphere and there's probably not going to be plenty of football for a lot of the match. You've got to earn the right to play."
Richardson, who is desperate to avoid the play-offs after losing out with Leeds in 2008, said: "It is important we go into it with very cool heads.
"It is easy to get carried away with the atmosphere and crowd and just lose it.
"We want to go over there and win."
Early pacesetters Charlton are five points adrift of automatic promotion and just four points ahead of Millwall in fifth place.
