Arsenal legend Ian Wright says Saturday's meeting with Tottenham is the biggest north London derby ever.
The fifth-placed Gunners are four points behind Spurs with a game in hand as they chase a Champions League berth.
"It doesn't get bigger than qualifying for the Champions League outright," Wright told BBC Sport. "The next four days make or break Arsenal's season."
Ex-Spurs skipper Gary Mabbutt agreed: "It really is a huge game, one of the most important Tottenham have faced."
Spurs have been in fourth place for most of the season and know victory in the last derby at Highbury would all but seal their European place.
Wright knows Arsenal cannot afford to slip up and cannot rely on winning the Champions League to book their place for next season.
"We need to beat Spurs to get closer and to try and cement this Champions League place in case it doesn't work out in the final - if they get there," added Wright, who was speaking at the launch of the Sure Fanzone World Cup venue in London.
"In my opinion this is the biggest north London derby ever.
"The semi-final of the FA Cup when we beat them 1-0 was a major game, but it will never match up to this one in terms of importance."
Mabbutt believes Spurs are now at a crucial point in their history: "All the games from now on are arguably the biggest set of games the club has faced," he told BBC Sport.
"That may sound like an over-the-top statement, but to get back among the elite of Europe you have to be in the Champions League, and we've not even been fighting for a European place in the last decade.
"Being in the Champions League - it offers great finances and means you can attract the best players around - would be massive for the club."
Goalkeeping legend Ray Clemence, who made 240 league appearances for Tottenham, says Spurs would be happy to take a point from the contest.
"Tottenham don't have to win it whereas Arsenal do," Clemence told BBC Sport. "And there is a massive amount at stake.
"It's not just a case of that fourth place and one side finishing above the other. There are also the financial implications of what Champions League will give.
"Spurs have not been in Europe for many years so the extra revenue will be a massive boost for them.
"Arsenal are moving to a new stadium and have got a massive financial commitment. I'm sure in their figures they will probably have looked at being in the Champions League."
Reporting by Chris Charles, Sam Lyon and Mandeep Sanghera.