The Gunners go into the encounter at the Emirates Stadium three points behind their local rivals in the Premier League table.
"It's massive because it's a derby and a must-win, especially for the fans and for the league," Sagna told the club's official website. "We know it's already important because they won their first two games and we want to catch up. We have the opportunity to do it and I think we're going to have a great atmosphere as well."
Arsenal secured their place in the Champions League group stage on Tuesday night with a 2-0 win over Fenerbahce.