HARTLEPOOL United suffered their fifth defeat in a row when they went down to promotion-chasing Chesterfield.
It looked bright for Pools when Luke James put them ahead with a neat 24th-minute finish for his 16th goal of the season.
But the Spireites were level within six minutes, Liam Cooper forcing the ball in from close range after a corner.
Chesterfield clinched the winner in the 49th minute, the unmarked Eoin Doyle lifting a looping shot into the far corner of the net.
Much was riding on the game and that seemed apparent in the opening stages, with both sides content to feel each other out.
Sam Collins made an assured start with two strong headers while home debutant Scott Harrison’s first touch in the sixth minute was a good one, a header against Marc Richards.
Andy Rafferty, preferred in goal to Scott Flinders, also had a fine firsty involvement with a good catch from a cross in the ninth minute.
Chesterfield won their first corner in the 14th minute and Pools their first three minutes later but neither came to anything.
Pools had their first effort at goal in the 21st minute when Jack Compton was high with a right-foot shot.
There was danger at the other end seconds later after Jack Barmby lost the ball, allowing Chesterfield to break. Dan Gardner swung over the cross which Rafferty palmed onto his bar and out for a corner.
And Barmby atoned for his lost ball in style three minutes later when he set up the Pools opener.
He picked up the ball from a throw-in and threaded through a ball to JAMES who ran into the area and his superb left-foot shot beat Tommy Lee into his right corner.
The first yellow card of the afternoon went to Spireites skipper Ian Evatt after going through the back of Harewood.
Chesterfield drew level on the half-hour.
Simon Walton had made several important challenges in the home half and from one on Gardner he was forced to concede a corner.
Gardner took the flag-kick and Pools could not clear, with LIAM COOPER firing past Rafferty from a few yards.
Pools were almost back in front from a corner of their own within two minutes but Collins saw a header nodded off the away line.
Sam Morsy was high wide and not very handsome with a 43rd-minute shot and Pools almost conceded a minute later when Compton lost the ball just outside the Chesterfield box.
The Spireites broke 70 yards up field and outnumbered the home side in the Pools box, but their final delivery was poor.
Pools made a terrible start to the second half, going 2-1 down in the 49th minute.
Daniel Kearns swung over a deep cross from wide on the left which Gardner kept in with some excellent control. He laid the ball back to the unmarked DOYLE whose looping right-foot shot went into the right corner of Rafferty’s goal.
Chesterfield made their first change in the 57th minute, leading scorer Gary Roberts replacing the injured Gardner.
It sparked several changes with Pools legend Ritchie Humphreys coming on for Chesterfield to huge applause from all four stands.
The Pools player of the century came on at left side of midfield for Kearns.
Pools boss Colin Cooper made a double change after 61 minutes, bringing on James Poole and Jon Franks for the ineffective Barmby and Compton.
Chesterfield remained on top with Pools struggling to get any momentum - or see anything of the ball.
Their afternoon was summed up when in a rare excursion into the away box, Harrison showed neat footwork to tee up a 72nd-miunute shot, only to see it rebound off Harewood.
Cooper made his final change 10 minutes from time, bringing on on-loan Sunderland player Connor Oliver for Brad Walker.
Oliver swept out a good ball for James, who was fouled by Cooper.
Pools flooded the box for Walton’s free-kick but when the ball came back out to the edge of the box, Oliver’s attempted pass to the far post went out for a goal-kick.
At the other end, Rafferty made a great save down to his left after Doyle had combined with Spireites sub Gnaduillet whose low shot was well hewld by the keeper.
Pools had a late, but brief, assault, Chesterfield doing well to intercept a long Oliver pass intended for Collins.
Chesterfield cleared under pressure at the corner, but it was to be their final scare as they played out four minutes of added time with comfort.
POOLS: Rafferty, Duckworth, Harrison, Collins, Holden, Barmby (Franks 62), Walker (Oliver 80), Walton, Compton (Poole 61), Harewood, James.
Subs: Flinders, Richards, Jones, Oliver, Hawkins, Franks, Poole
CHESTERFIELD: Lee, Darikya, Evatt, Cooper, Smith, ardner (Roberts 57), Morsy, Hird, Kearns (Humphreys 60), Richards (Gnanduillet 80), Doyle
Referee: Eddie Ilderton
Att 3778 (Away 553)