The Spireites twice took the lead but lost 3-2 against relegation fighting Leyton Orient as the O's grabbed an injury time winner.
Jay O’Shea’s early penalty gave Chesterfield the lead but David Mooney levelled for the visitors before half time. The home side regained the advantage early in the second half through an Elliot Omozusi own goal but Mooney once again equalised for the O’s.
Following a number of injuries the second half saw over eight minutes of additional time and it was deep into that time Dean Cox pounced on Tommy Lee’s dropped cross to net the winner.
Paul Cook made three changes to Chesterfield’s starting line-up from the team that lost to Preston in mid-week, bringing Charlie Raglan into the heart of the defence as Sam Hird serves his one match ban. Armand Gnanduillet was also back in the 11 with Birmingham City loanee Mark Duffy making his full debut in midfield.
Neither side were able to dominate in the opening minutes though Duffy looked to make an immediate impact, creating the first Spireites chance. Using his pace to drive down the left wing, he slid Sam Clucas into the Orient six-yard box but his chipped cross was cleared.
After a slow start the breakthrough came in the 19th minute as Chesterfield were able to cut get among the Orient defence for the first time.
Jimmy Ryan played a through ball to Caolan Lavery who cut inside his defender in the box, drawing the foul and seeing the referee point to the spot.
O’Shea stepped up, taking over the spot kick duties from Eoin Doyle, and calmly slotted the ball home low and to his left, wrong-footing the ‘keeper.
Lavery and O’Shea were at the heart of the action again moments later as the striker slid the ball across to O’Shea, whose curling shot warmed the palms of Alex Cisak in the Orient goal.
Orient were given the opportunity to equalise just after the half hour mark when Ian Evatt brought down Romain Vincelot to give the visitors a free-kick in a promising position.
Josh Wright curled in the free-kick which was cleared to the halfway line. From there the ball was lofted long to Chris Dagnall who had a free shot on goal from the left of the box but missed the ball as it bounced past him.
The Spireites defence was eventually made to pay in the 35th minute when Cox broke free down the left, bringing Lee out of his goal before squaring it to David Mooney. The Orient midfielder was under pressure from a back-tracking Spireites defender but tapped in from three yards out.
The visitors continued to pressurise the Spireites defence with long balls into the box, forcing Lee to come out and punch the ball away on more than one occasion.
The home fans were in fine voice as the second half began with Chesterfield needing to go through the gears in order to take all three points.
However, it was the away side who got the first clear-cut chance of the second half. After breaking free from both Evatt and Raglan he was only able to fire his shot high and wide.
The visitors were left ruing the missed chance as less than a minute later the Spireites were back in front through an own goal.
The Spireites worked the ball well on the edge of the area, with Ryan and O’Shea combining well. The move ended up with Gnanduillet playing the ball across the six-yard box and under pressure Omozusi fired into his own.
Seconds after his involvement in the Spireites’ second, the Ivorian striker had the ball in the back of the net again, but this time ruled out for a foul on the Orient ‘keeper.
After regaining the lead Chesterfield began to control the game but just as they asserted themselves they allowed the visitors to equalise again.
A hopeful ball over the top allowed Mooney to break the offside trap before finishing calmly low past Lee to score his second of the game.
Orient had a chance to steal the game in the dying minutes of normal time when skipper Nathan Clarke rose highest from a corner to direct a header towards the far corner of Lee’s goal. The Spireites ‘keeper had to scramble back but was able to tip the ball round to the post.
The eights minutes of signalled additional time were extended after a head injury to Evatt and he was forced to come off the field with the Spireites down to ten men having already used their three substitutions.
In the dying seconds of stoppage time the game then swung in Orient's favour as Lee stretched and failed to hold onto a high cross from the right. The ball fell kindly to Cox who slotted home from two yards out to give Orient all three points.
Chesterfield FC: Lee (gk) – Darikwa, Raglan, Evatt (c), Clucas – O’Shea, Morsy, Ryan (Humphreys 78’), Duffy (Jones 75’) – Gnanduillet (Harrison 82’), Lavery
Subs not used: Chapman (gk), Banks, Dieseruvwe
Leyton Orient FC: Cisak (gk) - Omozusi, Clarke (c), Vincelot, Sawyer – Pritchard (Hedges 67’), Lowry, Wright (Bartley 58’), Cox – Dagnall, Mooney (Batt 83’)
Subs not used: Baudry, Lisbie, McAnuff, Woods
Chesterfield: O’Shea 19’, Omozusi OG 54’
Leyton Orient: Mooney 35’, 70’, Cox 90+11'
Attendance: 6,524 (285 away supporters)