Walsall surrendered top spot in League One after losing at home to Chesterfield.
Sylvan Ebanks-Blake’s early header put the Spireites ahead before Ian Evatt converted Dan Gardner's corner to make it 2-0 on 54 minutes.
Matt Preston pulled a goal back in stoppage time, but Chesterfield held on to condemn the Saddlers to a first defeat in seven league matches.
Walsall are now second in League One, two points behind new leaders Gillingham, who claimed a last-gasp 1-0 win at Crewe.
Dean Smith made three changes to the side that beat Burton 2-0 last weekend.
Returning internationals, Neil Etheridge and Jason Demetriou, came into the starting XI, along with young defender Matt Preston. Craig MacGillivray and Liam Kinsella dropped to the bench, while James O’Connor missed out because of a tight groin injury.
Spireites stopper Tommy Lee was called into action within the opening minute, diving to his left to push away Tom Bradshaw’s low shot from an acute angle.
That chance sparked Chesterfield into life and on five minutes they went in front.
Chris Herd was the architect, delivering a deep cross from the right towards Ebanks-Blake in the middle.
The former Wolves striker pealed away from his marker and headed into the top corner from eight yards.
The Spireites enjoyed a concerted spell of pressure following the goal, but Walsall gradually worked their way back into the contest and began to dominate.
Reece Flanagan, Andy Taylor and Bradshaw each saw attempts blocked, and Rico Henry fired narrowly wide with a low drive from outside the box.
On 28 minutes, Paul Downing, Mantom and Demetriou linked up smartly down the right.
Demetriou reached the byline and picked out Bradshaw with a pinpoint low cross but the striker’s sweetly-struck volley was parried by Lee at his near post.
Walsall came within inches of an equaliser four minutes later.
Romaine Sawyers’ elegant flick teed up Mantom to unleash a low 25-yard drive which Lee did superbly to tip onto an upright.
HALF-TIME: WALSALL 0-1 CHESTERFIELD
The Saddlers were again denied by the woodwork at the start of the second half, when Adam Chambers’ long-range strike deflected off a visiting defender and rattled the post.
On a rare foray into Walsall territory, Spireites striker Lee Novak dragged a low shot wide of Etheridge’s right-hand upright from inside the area.
Against the run of play, Chesterfield doubled their advantage on 54 minutes.
Ebanks-Blake broke into the box and collided with Etheridge, who then received lengthy treatment to a gashed knee.
From Dan Gardner’s resulting corner, Evatt rose highest at the far post to send a thumping close-range header into the roof of the net.
It was turning into a frustrating day for the Saddlers.
Midway through the half, influential midfielder Mantom was carried off on a stretcher with an ankle injury. Taylor also limped off due to a knee problem.
Walsall were struggling to find a route back into the match.
Henry cut inside from the left before shooting wide, substitute Kieron Morris found the arms of Lee with a half-volley, and the former then blazed over.
The hosts continued to push forward in the closing stages, with Lee denying Demetriou at his near post and Milan Lalkovic curling wide after a short corner routine.
Walsall gave themselves a lifeline in the third minute of added time, when Preston bundled home from close range after Jordan Cook’s header had crashed against the bar.
However, it came too late to inspire an improbable comeback as Chesterfield held on for the win.
FULL-TIME: WALSALL 1-2 CHESTERFIELD
Team: Etheridge, Demetriou, Taylor (Morris 74’), Downing, Chambers ©, Mantom (Lalkovic 66’), Bradshaw, Sawyers, Henry, Preston, Flanagan (Cook 45’).
Subs not used: Baxendale, Forde, MacGillivray, Kinsella.
Attendance: 4,766 (399 Chesterfield supporters).