The Spireites go into the final match of the season in a campaign-highest spot of eighth but a frustrating four points off the play-off zone.
Despite a solid victory in the club’s first ever visit to Fleetwood, Bradford City nicked a single goal at home to Burton Albion.
That means Paul Cook’s men are unable to catch the Capital One Cup finalists, so will have to endure another basement season starting on August 3.
Sub Armand Gnanduillet headed Chesterfield into the lead in the 44th minute towards the end of a half that could have seen plenty more goals from both sides. He steered the ball into the roof of the net after Conor Townsend’s right-sided corner was knocked back by Neal Trotman.
That lead was doubled soon afterwards. Trotman was again involved, hitting a long ball for Gnanduillet to knock down to Marc Richards. The striker unleashed a storming first-time shot from the box edge that gave Scott Davies no chance.
With the game in its final third, the points were wrapped up. Jay O’Shea, whose footwork throughout had been fast and confusing for his markers, darted forwards before laying a skilful ball on for Sam Togwell. The midfielder slid in, forcing Davies to parry and the loose ball rolled to Richards, a yard inside the box this time. With his left foot he unleashed another first-time unstoppable hit to show what might have been had his season not been punctuated with minor injury after minor injury.
Lively sub Andrew Mangan, a player much admired by Cook, latched on to a David Ball low pass. He looked marginally offside but the officials didn’t agree. The striker controlled the ball, drew Tommy Lee and slotted in what turned out to be merely a consolation.
Cook couldn’t hide his disappointment at how the season has all but concluded: “I’m hugely disappointed. We’ve been inconsistent and that’s been our downfall. Overall, the league tables don’t lie. I’m absolutely devastated.
“I’ve never felt so sick after winning a game. We missed out today, but you’ve got to take your hat off to our support. I can guarantee our supporters that this club will get the success it deserves.
“Our club is run by a really good chairman and backed by a fantastic board. They won’t leave a stone unturned until this club gets some kind of success. They will get what they deserve. The positive for us today is our support. I take my hat off to them.”
Chesterfield went into the game knowing nothing less than a win was acceptable and, backed by around 1,500 fans in the highest league crowd yet seen at Highbury, they started on the front foot.
Former Spireite Alan Goodall, not one for shirking his tackling responsibilities, took just 45 seconds to enter the book for a lunge on O’Shea.
Richards was then bundled over by the keeper, but there was to be no first league penalty of the season for the visitors.
Ryan Crowther’s left-sided shot forced Lee to dive to save and he then had to block Gareth Evans.
For the first time the Cod Army took control of the game, forcing Spireites to make several positional changes with Drew Talbot in particular switching regularly. He started on the left wing, moved to the right and then took on a striking role. When Richard Brindley was withdrawn with a groin problem, he went to right-back.
The introduction of Gnanduillet changed the game. A 34th-minute entrant into the game, by the break he’d had a hand in both of the visitors’ goals.
Richards’ second was soon followed by the goal from a man who made his league debut as a 17 year old for Blackpool at Saltergate in 2004, but from then on Chesterfield were solid and never looked like seeing their lead threatened.
Fleetwood (4-4-2): Davies 6, Beeley 6, Goodall 6, Edwards 7, Brown 7, Ball 7, McKenna 6, McGuire 5, Crowther 7, Evans 5 (Fontaine 81), Matt 7 (Mangan 53, 7). Subs (not used): Lucas, Barry, Pond, Nicholson, McLaughlin.
Chesterfield (4-4-1-1): Lee 7, Brindley 6 (Gnanduillet 34, 7), Trotman 7, Cooper 6, Townsend 6, Darikwa 5, Togwell 6, Randall 5 (Hird 73), Talbot 7, O’Shea 8 (Henshall 83), Richards 7. Subs (not used): O’Donnell, Whitaker, Clay, Boden.
Goals: Mangan 68 (Fleetwood), Gnanduillet 44, Richards 45+2, 63 (Chesterfield).
RefEREE: Andy Davies (Merseyside).
Bookings: Randall (Chesterfield), Goodall, Brown (Fleetwood).