The Spireites earned a crucial 1-0 win over Walsall as Sam Hird's late header secured all three points for the hosts at the Proact.
A tepid first half where both teams looked good in the first two thirds but not the third gave way to a second half with plenty of effort but not quite enough inspiration, that was until five minutes from time when Hird rose to head home Jimmy Ryan's corner to win the game for Chesterfield.
The Spireites opened up the match looking to attack and midfielder Jay O'Shea had the first chance when a short free kick gave him space to glide into, though his eventual shot was high and some way over the bar.
The early minutes were open and despite Walsall's tag as low scorers the match promised much, Walsall's Andy Taylor finding space down the left before seeing his cross well blocked by Tendayi Darikwa, the resulting corner was headed away by Ian Evatt - making his 150th appearance for the Spireites in the match.
Ollie Banks thought he had opened the scoring for the Spireites after eight minutes, pouncing on his own rebound to put the ball in the back of the net, but his celebrations didn't manage to get underway as the referee had adjudged that his opening headed effort came only after a push on his marker.
Walsall had their first shot when Anthony Forde forced a long-range effort well wide, with O'Shea then under but not quite close enough with his head to a swung-in Banks corner.
Banks was among the action again as he headed narrowly over the crossbar when Drew Talbot crossed for the midfielder to stoop and threaten an opener with his head.
The match was still bubbling under somewhat but Saddlers striker Jordan Cook swivelled to send a shot not too far wide of Tommy Lee's far post when allowed space on the edge of the Spireites box.
At the other end a combination of a deflection and a gust of wind 27 minutes in took a Roberts cross close to heading straight in, before finally drifting wide for a home corner.
With Chesterfield beginning to get on top of their opponents, captain Sam Morsy stung the palms of former Spireites 'keeper Richard O'Donnell when he fired in a powerful effort from 25 yards ten minutes before the break.
An acrobatic Sam Clucas next threatened as he ran and jumped onto Darikwa's wicked ball in, but was unable to connect with his flying volley as the game ended for the first half without a goal, though Jordy Hiwula headed wide on the stroke of half time.
The second period took time to get going, Banks wriggling into the box but the ball nipped off his toe at the last when the Spireites had already beaten two men.
Just before the hour mark and the hosts were doing their best to put the pressure on, Roberts dummying his way past a Walsall defender before playing a ball through for Clucas that was just a good first touch away from opening up the visiting defence.
Moments later and defender Hird scuffed wide a recycled corner when a truer contact would have opened the scoring from eight yards out.
With substitutes coming thick and fast, Walsall went close to opening the scoring when James Chambers looped a header onto the crossbar, via a fine tip from Lee. Darikwa was then sharp to follow up off the woodwork to clear.
The visitors went close again when Hiwula flicked an instinctive effort goalwards and onto the post, the chance coming out of the blue.
With just five minutes remaining and the game seemingly destined to end without a goal, an arrowed Jimmy Ryan corner found its mark at the back post with Hird heading towards the turf with accuracy and power to beat the 'keeper.
The goal woke up the Proact and the Spireites comfortably hung on to their lead to claim an all-important three points in their quest for the play-offs.
Chesterfield: Lee (gk), Darikwa, Hird, Evatt, Talbot, Morsy (c), Ryan, O'Shea (Dieseruvwe 69'), Banks (Ariyibi 61'), Roberts (Harrison 69'), Clucas
Subs not used: Flatt (gk), Raglan, Carter, Humphreys
Walsall: O'Donnell (gk), Purkiss, Taylor, O'Connor, A. Chambers (c) (Flanagan 82'), Mantom, Baxendale (Benning 61'), J. Chambers, Cook, Forde (Cain 61'), Hiwula
Subs not used: Downing, MacGillivray, Grimes. Murphy
Chesterfield: Hird 86'
Attendance: 6,358 (460 away fans)