It came courtesy of Mike Jones in the 78th minute.
He received the ball from livewire midfielder Matty Palmer, partially turned, looked to shoot, took another couple of paces forwards before shooting low from the box-edge beyond the outstretched right hand of Tommy Lee.
In a game punctuated with poor passing and a huge amount of throw-ins, a single goal always looked enough to nick the points and Jones’ strike only confirmed that.
Late on, Chesterfield threw plenty of men forwards but they lacked the quality and composure needed to get an equaliser.
Gboly Ariyibi forced goalkeeper Joel Coleman to tip over a deep cross from the right but he was only rarely tested by Spireites’ frontmen, something that will frustrate Danny Wilson on a day when too many of his players failed to show enough quality.
Wilson made three changes to the side that played out a goalless draw with Fleetwood Town on Saturday; Ollie Banks, Jay O’Shea and Chris Herd dropped to the bench and were replaced by Sylvan Ebanks-Blake, Charlie Raglan and Jamal Campbell-Ryce, with Sam Hird switching to midfield.
A nervous first half on a sand-dominated pitch featured limited Chesterfield attacking; only a shot that went well over from Ariyibi and a cross from Ebanks-Blake that clipped the bar and was spooned away by Coleman moments worthy of note.
John Sheridan’s Oldham had the majority of the ball ahead of the break and created two more than decent openings. Jonathan Forte crossed from the left for Aaron Holloway but the striker failed to make contact with the ball at the far-post, when only a yard out, whilst Lee had to save from Curtis Main’s close range shot.
The dangerous Holloway was carried off in the second half after an awkward fall and his replacement provided the game’s quality moment for the goal; sub Tommy Thiele was also subbed late on with an arm injury to further deplete Oldham’s squad for the run-in.
Striker Jake Orrell came on to make his League debut and was very much in evidence in his few minutes on the pitch, but like his colleagues, was unable to carve open any gilt edged chances when it counted.
Blackpool’s win at Doncaster Rovers means that Spireites’ home game with Rob Page’s Port Vale on Saturday becomes a must-win encounter and before, then Wilson will have to find the right recipe for goals that’s been frustratingly lacking over Easter against two relegation rivals.
Oldham: Coleman, J.Wilson, B.Wilson, Gerrard, Holmes-Dennis, Dieng, Kelly, Palmer, Main, Holloway (Jones 60), Forte (Thiele 71) (Cassidy 90+1). Subs (not used): Cornell, Mills, Croft, Winchester.
chesterfield: Lee, O’Neil, Raglan, Anderson, Talbot, Ariyibi (Orrell 89), Hird, Liddle, Campbell-Ryce (O’Shea 56), Novak, Ebanks-Blake (Slew 66). Subs (not used): Chapman, Herd, Banks, Humphreys.
Ref: Tony Harrington (Cleveland)
Bookings: Anderson (Chesterfield)
Attendance: 4483 (599 from Chesterfield)