The one constant in the English Premier League is that no matter what else happens, Arsenal will finish in the top four. Under manager Arsene Wenger, the club has never finished as low as fifth, a run dating to the 1996-97 season. After 21 years, Arsenal may finally drop outside the top four. The Gunners are currently in fifth place with only a 22 percent chance of fighting their way back into the top four.

The implications for Arsenal go well beyond just the trivia. First, it would cost the North London club an annual influx of cash it has grown accustomed to. The top four clubs in the Premier League qualify for the Champions League, which provides a major revenue boost; last season Arsenal made about $58 million from the Champions League. If Arsenal finish outside the top four, the club will qualify for the Europa League, where Tottenham Hotspur earned almost $23 million last season for a similar performance.

It may also cost them players. Playing in Europe’s premier club tournament offers prestige and glory that in turn helps attract better players on transfers. Arsenal should be particularly worried about maintaining their Champions League streak because star forward Alexis Sanchez has only one season remaining on his contract. If Sanchez does not sign a new contract this summer, he may have to be sold in order for Arsenal to recoup a transfer fee from his departure. The sharks are already circling, with Bayern Munich, Paris Saint-Germain, Juventus and Chelsea rumored to be considering bids.

But the most significant casualty of Arsenal’s disappointing season may be Wenger himself. The long-tenured manager has not signed a contract for next season. If Arsenal cannot right the ship, he may be gone, ending an unprecedented run of consistency at the top. (Since he took the reins at Arsenal, 159 different coaches have held a job in the EPL, plus another 53 have held interim positions.)

So with three Premier League games remaining for most of the teams at the top of the table, the stakes could hardly be higher. With yesterday’s victory at Southampton, Arsenal remained in the top four race with a 22 percent chance of Champions League qualification. To get there, Arsenal will need Liverpool or Manchester City to drop points, and the Gunners will probably need to win all of their remaining matches. Arsenal projects to a 61 percent chance of finishing in the top four if it wins out, with chances falling fast if any more points are dropped.

So how has Arsenal found itself in this predicament? The streak is evidence that the team hasn’t had a really bad spell in decades. But that doesn’t mean the team has gotten any better — and that’s part of the problem. Wenger’s Arsenal for years has treaded water in the third- and fourth-place spots — last season was the first time Arsenal had finished above third since 2005. All it would take for the Gunners to fall would be for the other big clubs in the Premier League to play up to expectations. And this season that is exactly what has happened.

Arsenal has taken 66 points through 35 matches with a plus-26 goal difference. These numbers are not particularly unusual for Arsenal in the last several seasons. Since 2010-11, Arsenal’s points through 35 games have ranged from 64 to 70. The goal-difference numbers are ranged similarly, from plus-21 to plus-32. The Gunners’ stats this season show up at the lower end of the team’s recent level, but they are not outliers.

What has changed is the rest of the Premier League. The average points taken by the other big clubs (Chelsea, Liverpool, Manchester City, Manchester United and Tottenham) this season through 35 games was 72.8. In previous seasons this average has not exceeded 70. Among the weakest four of the big six, the clubs Arsenal directly needs to beat in order to qualify for the Champions League, the average point total through 35 matches this year is 67.7. Only once previously (2013-14) has the average been close, and Arsenal was fortunate enough to be clear with 70 points through 35 matches that year.

The strategy of Wenger’s Arsenal has been to build a team good enough to reach the top four, usually with 70-75 points and a goal difference between plus-20 and plus-30. The strategy has worked in part because the other clubs with the resources to match these results failed to achieve Arsenal’s consistency. This year they have improved and Arsenal has not.

But that is not the whole story. Expected goals, a statistical measure of the quality of chances created and conceded, suggests that Arsenal in 2016-17 are running below the level of quality they have in the recent past. Arsenal’s expected goals difference is only plus-13, easily the club’s worst statistical performance in the last six years. This drop-off has been most pronounced in recent weeks. Since March 1, Arsenal has gone 5-1-4, but the Gunners have conceded as many goals as they have scored. Their expected goals difference is even worse, at minus-4.

The most notable change in this time is that Wenger has, for the first time in years, switched to a formation with three center backs, utilizing winger Alex Oxlade-Chamberlain as a wingback and deploying a varying set of forwards — including Sanchez, Mesut Ozil, Olivier Giroud, Danny Welbeck and Theo Walcott — in a front three. Playing in the new formation has brought a good haul of points, but in those matches Arsenal has conceded more clear scoring chances to its opponents (9) than it has created (5). The streak is unlikely to continue unless the underlying performances pick up.

What is most notable about the changes in formation and personnel is that Arsenal usually isn’t tinkering this late in the season. Wenger is known for giving his attackers freedom to improvise on the pitch and to build off relationships and experience. It stands to reason that in such a system, stability in personnel and tactics would lead to higher levels of performance, as players develop understandings from playing together. Arsenal’s statistics over the last six years bear this out. During seasons in which Arsenal has maintained stability in its first 11 over the final weeks of the season, the club has finished hot. In the only two seasons when Wenger made major changes, Arsenal has averaged just 1.6 and 1.1 points per match, respectively, down the stretch.

Regardless of whether Wenger continues to tweak tactics in these final three games, his team needs to win — and even that may be not be enough. With luck, perhaps these new tactics and new formation will click and the streak can be extended. But if it doesn’t pull off late-season heroics, Arsenal won’t be seen in the Champions League next fall, and the team that will be seen in England may look much different.