The Canaries have won two of their last three games, including a victory over Manchester United at Old Trafford plus a home success against Aston Villa earlier this week.
Furthermore, Alex Neil’s side have not lost at home since late October, leaving Koeman anticipating a tricky match.
“I was watching the game that they played last, against Aston Villa at home, and they are strong.
“They have a confidence now that they can beat [teams]. They won away against Manchester United, and that gives teams like Norwich a big belief and a big confidence to battle to stay in the Premier League. That's one of the reasons why it's a difficult game.
“They are fighting to keep their position in the Premier League. They are strong at home and they're an aggressive team so it's a difficult one, but we need to win.”