Arsène Wenger puts Crystal Palace's recent improvement down to their defensive stability.
The Eagles have kept seven clean sheets from their past 13 games and their midweek win over Hull City sent them four points clear of the relegation zone.
Palace's last visit to north London ended in a 2-0 defeat against Tottenham but Wenger says they were "absolutely impressive" that day.
I saw them play against Tottenham - they were absolutely impressive in that gameArsène Wenger
"They have a stronger belief certainly," Wenger said. "They don't concede goals, they have a very efficient game and recently they had consistent results so it is for us and for them a very important game.
"They are recovering well because they are stable defensively. I saw them play against Tottenham - they were absolutely impressive in that game. That is a good warning for us."
Former Gunner Marouane Chamakh returns to Emirates Stadium for the first time since his summer move to Selhurst Park and Wenger is pleased that the Moroccan striker is playing regular football.
"Chamakh is doing very well and I'm happy for him because we love him here," he said. "He had a great start here in the first six months.
"After [Robin] van Persie came back, he had an impossible competition because Van Persie is world class and it was very difficult for him to compete.
"He didn't play anymore and didn't have exactly the career he expected to have here. He is a great guy, a great player and I am very happy it is going well for him."Copyright 2015 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source