Arsenal missed out on a top-four finish for the first time in Arsene Wenger's 21-year reign as manager, despite a 3-1 win over Everton at the Emirates Stadium on Sunday.
Yet the Gunners' fate was decided elsewhere as Liverpool beat already relegated Middlesbrough 3-0 at Anfield to seal fourth place and the Premier League's final qualification spot for the Champions League.
It means the Gunners won't play UEFA Champions League football next season and must settle for a place in the UEFA Europa League instead. Arsenal haven't started a season in Europe's second-tier competition since 1997, while their fifth-placed finish is the lowest since the 1995/96 campaign, one season before Wenger's arrival.
Goals from Hector Bellerin and Alexis Sanchez, either side of Laurent Koscielny receiving a red card, put Arsenal two up against the Toffees at half-time. Romelu Lukaku got one back for Everton from the spot after the break, as the Gunners lost another defender, Gabriel, to injury.
Aaron Ramsey scored in stoppage time to ice Arsenal's eighth win in nine matches in all competitions, a run that ultimately counts for naught.
Wenger had replaced Shkodran Mustafi with Gabriel in his back three, while Danny Welbeck came in to lead the forward line in place of Olivier Giroud, per Arsenal's official Twitter account:
Meanwhile, Everton boss Ronald Koeman put Enner Valencia in attack alongside Lukaku, per the club:
The Gunners were nearly in front on two minutes when Sanchez played in wing-back Bellerin, whose cross reached Welbeck, but the striker glanced it wide.
Still, Arsenal soon made good on their fast start, with Welbeck and Bellerin again heavily involved in the eighth minute. The former hit air when he would have had a tap-in from Ozil's low cross, but Bellerin was on hand to apply the finish and temporarily put the Gunners into the Champions League places as things stood.
Arsenal should have been coasting, but disaster struck on 14 minutes when Koscielny rashly left his feet in a tackle against Valencia. Referee Michael Oliver wasted little time showing the French centre-back a straight red card.
BBC Sport's Phil McNulty lamented Koscielny's dubious decision-making while also spelling out the worrying implications of the red card for the Gunners beyond this game:
Meanwhile, OptaJoe noted how picking up red cards in the league has become a troubling habit for Koscielny:
Needing the security of a second, Arsenal went close on 24 minutes as Gabriel rose highest to meet a corner but powered his header wide. The Brazilian was now alongside Rob Holding in a more traditional back four as Wenger rearranged his team on the fly without Koscielny.
Fortunately for the Gunners, their security arrived three minutes later when Sanchez, the club's likely player of the season, converted from close range after Welbeck rolled him in. Endeavour got Sanchez his goal, but James Olley of the London Evening Standard noted how the Toffees switched off at a key moment:
Arsenal held on until the break, with Petr Cech making saves from both Lukaku and Valencia. However, bad news broke just before half-time when Liverpool took the lead at Anfield in first-half stoppage time, knocking the Gunners out of the top four as things stood.
The second half started with Joel Robles making a double save to deny Welbeck and then Ozil, with Sanchez again at the heart of Arsenal's attacking play.
Speaking of a double, a two-fold blow came the Gunners' way six minutes into the second half when Philippe Coutinho doubled Liverpool's lead at Anfield while Gabriel went down with an apparent knee injury.
The former Villarreal man left the pitch on a stretcher as Arsenal's defensive resources got thinner. Per Mertesacker replaced him.
There was more frustration for the home crowd when Everton centre-back Ashley Williams escaped what should have been a second yellow card after bringing down Welbeck when the striker appeared clean through.
John Cross of the Daily Mirror was left shocked by the referee's unwillingness to at least book Williams:
Things got worse for Arsenal when Lukaku converted from the spot two minutes before the hour mark. Everton won the spot-kick when Holding was adjudged to have handled in the box.
Cross took the opportunity to again bemoan Oliver's decisions:
The ref was again under the spotlight when Toffees midfielder Morgan Schneiderlin escaped a second booking after tripping Ozil. Yet it was Everton who soon felt aggrieved by Oliver when an apparent equaliser was chalked off for what was deemed a foul by Valencia in the buildup.
Arsenal nearly restored their two-goal cushion when Ramsey played Ozil in, but Robles saved well again. Moments before, Sanchez had to be replaced by Alex Iwobi after some rough treatment from the visitors.
Ramsey scored in stoppage time to ice what was ultimately a hollow win for Wenger's men.
Missing out on the Champions League only underlines the uncertainty surrounding Arsenal this summer. Wenger is out of contract, while the futures of star players Sanchez and Ozil still need to be decided.
The calls for change will only grow louder now Wenger has lost the security of his regular top-four finish.
Wenger opted not to take part in Arsenal's traditional, end-of-season lap of honour, per Olley. Instead, the Gunners boss revealed afterwards how doubts about his future have contributed to the difficult atmosphere his team has played under in 2017, per BBC Sport:
"I believe since January we have played in a very difficult environment for different reasons.
Some you know about and that's very difficult for a group of players to cope with that - and some other reasons we will talk about on another day.
Psychologically the atmosphere was absolutely horrendous. It has been difficult, yes, and certainly my personal situation has contributed to that but you can never question my professionalism or commitment."
Wenger also underlined his commitment to the Gunners, per James Benge of the London Evening Standard: "I am professional. As long as I’m somewhere I do my job until the last day. You could not question my love or loyalty to this club. I said no to every club in the world to stay here with very restricted finances for years."
Surprisingly, Wenger also reaffirmed his belief his current squad is strong enough to win the Premier League title, per an interview with TalkSport: "No matter what happens, I’m convinced this group will win the Premier League (either) next year or (in the future). If you keep them together they will be a force next year."
Wenger will know how tough it will be for this squad to compete for major prizes if Sanchez and Ozil, whose contracts expire in 2018, leave this summer. Securing their futures is just one of the many difficult decisions now facing Arsenal.