Sokratis Papastathopoulos believes Arsenal's spirit was "perfect" ahead of the north London derby and it will be key if the side is to secure one of the Premier League's top-four spots this season.
Arsenal could only take a 1-1 draw from Wembley on Saturday, as Pierre-Emerick Aubameyang saw a 91st-minute penalty saved by Tottenham goalkeeper Hugo Lloris.
Had the Gabon striker converted, the Gunners would have moved back above fourth-place Manchester United and to within just a point of Spurs.
However, Unai Emery's side appears to have turned a corner in the Premier League since losing to Manchester City on February 3, winning three and drawing one, and Sunday's visit of United could go a long way to determining the two teams' final positions.
And according to Sokratis, the mentality instilled by coach Emery could be vital.
"The spirit of the team was perfect [against Tottenham] and before the game our manager said that this will be our strong point [on Saturday], the spirit," the Greek defender told reporters.
"It's not about how we play. It's also that we all, everybody, believe that we can do it. This is very important for the team, for the spirit.
"Every day in training we know that we are there and it's very important for us. We win together, we lose together, we are one team, and we have to go on like this in the next games.
"It's very important for us and for our manager that we take one of the four positions so that next year we are in the Champions League.
"I think that we had in the beginning of the year a lot of injured players. Of course, it was a new team, new coach, new manager, new things. Every game, every month that is coming, I think that we will be much better.
"Now that it [the season] is coming to the end, every point counts and every minute we have to give 100 per cent."