Walcott, 22, insists the mood among the players is far better than when they were humiliated 8-2 at Old Trafford in August.
He told Match of the Day Magazine: "We're making the Emirates into a fortress now.
"We're coming back in games we might have lost before. The top teams are not dropping many points so we need to win.
"The atmosphere in the dressing room is unbelievable. We have some great leaders as well.
"You ask any player here and they'll tell you it's the best it's been for a long time."