The Gunners are unlikely to progress past the round-of-16 stage following their first-leg 3-1 defeat to the Bundesliga outfit at the Emirates last night.
"We need to try and not dwell on this result," Walcott told the club's official website. "We need to think about getting back to the Premier League. We've got some important matches coming up thick and fast."
Arsenal's next three league clashes are against Aston Villa, Tottenham Hotspur and Everton.