Two second half goals from Niall Canavan and Paddy Madden sent Chesterfield to defeat. Spireites put in a decent first half show but were undone from a corner and then conceded a late killer goal as they pushed to level.
Paul Cook made five changes to his starting XI in a bid to avoid a third consecutive defeat, returning to his favoured formation.
Ian Evatt was forced out after losing consciousness briefly towards the end of Saturday’s loss at home to lowly Orient.
Onto the bench went fellow centre half Charlie Raglan, winger Mark Duffy plus strike duo Caolan Lavery and Armand Gnanduillet.
Skipper Sam Hird returned after serving a one match ban for his red card against Preston whilst new striker Byron Harrison was given the starting shirt up front on his own as the manager reverted to 4-2-3-1 for the first time in 2015.
Ritchie Humphreys came in to the attacking midfield three whilst the two surprise selections saw rapid raider Gboly Ariyibi and Ashley Carter come in; Carter, 19 and on loan from Wolves, made his senior bow as left sided central defender. Sam Morsy was skipper.
Mark Robins’ Iron were unchanged though ex-Blade Isaiah Osbourne returned to the bench after injury.
Former Spireite Gary McSheffrey missed out due to suspension whilst his replacement, Dutchman Kevin van Veen, signed last month from FC Oss, was a transfer window target of Chesterfield.
Spireites started slowly but carefully though debut maker Carter had to head a Van Veen effort off the line early on and Tommy Lee had to make a sharp save to deny Paddy Madden.
Ariyibi showed fancy footwork galore to go with his undoubted pace and he delivered several decent crosses showing there can be positive output from his trickery whilst Carter showed great maturity, barring some loose distribution when he switched to attacking mode.
Lee had a couple more decent saves to make from Madden and Van Veen whilst O’Shea, Harrison and Morsy all warmed the palms of Luke Daniels.
Cook will have been satisfied with his troops at the break, calling for just a little bit more thought in final third possession whilst he’d no doubt have encouraged Harrison to take a few more risks.
Canavan’s 58th minute header from a left sided corner exposed Chesterfield’s achilles heel again, Gnanduillet had been sent on immediately after the corner was awarded to mark Canavan but he was unable to pick up the big Irishman.
Madden’s late strike following a pass from the impressive Liam O’Neil was hammered home from an angle, sub Dan Jones will have been disappointed not to have cut the ball out and from then on the contest was over.