The Blues were in danger of being caught in fourth place in the Premier League.
But a valuable home three points means they maintain the gap to other teams, and extend it by three points over Spurs.
And Giroud, who scored the first goal in the 2-1 win on Saturday, thinks it can turn around their season.
"It was a very important game for us," Giroud told reporters.
"I want to talk about the team spirit. We showed great character.
"We knew it was maybe a kind of turning point because we lost a bit of confidence at home.
"It was nice to bounce back and get this hard win against a rival."