This was one of those games dubbed ‘must win’ by anyone looking at the table with a sense of realism, and the Spireites were leading 1-0 with 12 minutes remaining.
But a cruel twist and a breathless period of late drama saw them miss a sitter, go down to 10 men and concede twice.
The manner of Bury’s winner will particularly rankle with supporters, debutant keeper Thorsten Stuckmann failing to deal with a tricky back pass and gifting the ball to George Miller who found an empty net to send his side out of the relegation zone.
It was a scenario that seemed nigh on impossible at the break, Chesterfield ahead through a Kristian Dennis goal and looking comfortable.
But late goals have been all too common and have played a big part in the Spireites’ struggles under two sets of management teams.
The present incumbent, Gary Caldwell, looked to have got things spot on in the first half with his formation, tactics and selection paying off.
Sylvan Ebanks-Blake, making his first league start of the season, was a handful for Bury and had already been involved in two good chances before he set up the opener.
His sublime lofted ball allowed Dennis to race in on goal and the striker bobbled it past Joe Murphy for a deserved Town lead.
Lee Clark’s Shakers had a couple of half chances in the first period but were hampered by wayward finishing.
They came out for the second and dominated, aided by a Chesterfield who failed to get to grips in midfield and showed no composure on the ball, inviting pressure.
The woodwork, Tom Anderson and Sam Hird had all come to the hosts’ rescue before the pressure finally told.
Anderson fouled Ryan Lowe in the box and was, perhaps harshly, sent off.
Stuckmann saved the spot-kick and then within 60 seconds was picking an Andrew Tutte wonderstrike out of his net.
And worse was to follow, Reece Brown’s poor header putting Chesterfield on the back foot, Hird’s back pass too strong for Stuckmann whose heavy touch was gleefully accepted by Miller, the substitute rounding the keeper to score the winner.
As unthinkable as a 2-1 defeat might have been at the interval, late collapse has almost become an inevitable theme for a Town side who have taken just seven points from eight games against their fellow bottom six sides.
This defeat leaves Town seven points adrift of safety with 14 games to go – not down yet, but they’re certainly punchdrunk and on the ropes.
Chesterfield: Stuckmann 6, Kakay 4, Jones 6, Anderson 6, Hird 6, Evatt 7, Grimshaw 6, Gardner 5 (Brown 63), Dennis 6 (Mitchell 67), Faupala 5, Ebanks-Blake 6 (Simons 71). Not used: Martinez, Humphreys, El Fitouri, Allinson.
Bury: Murphy 7, Leigh 8, C. Burgess 7, Kay 6, Tutte 7, Pope 5 (Miller 54), Melis 6, S. Burgess 6 (Styles 63), Barnett 6, Moore 7, Lowe 7 (Hope 86). Subs: Williams, McGreath, Pennant, Deslands.