Neil Harris’ side are seven points adrift of safety with five games remaining, but Friday’s dramatic 2-1 victory over derby rivals Charlton at The Den has lifted spirits in the camp.
It was the Lions’ first win on their own patch since October and they now face back-to-back home games against Watford and relegation rivals Wigan.
Upson told the club website: “The feeling at the end of the game on Friday was elation; you could see what it means to the fans and to us out on the pitch too – and especially against that team in particular. It was a great feeling all round.
“We showed true character which I think the manager has instilled in the squad. There is a real sense of belief here.”