The Spireites will have to wait for another top-six confirmation day after Rochdale beat Leyton Orient 1-0 at Spotland to keep their play-off hopes alive.Dale striker Ian Henderson scored the game's only goal just past the hour mark to move his side within five points of Chesterfield with two games left to play.
Spireites manager Paul Cook was in attendance at Spotland, knowing that if Rochdale failed to beat Leyton Orient then his side would be confirmed in this season's Sky Bet League 1 play-offs.
Leyton Orient started with hunger, Marvin Bartley going close before Henderson twice went close for the hosts - his second effort a glancing header from a corner only just over the Orient bar.
Midway through the half and Peter Vincenti went close with a header that flicked up and landed for Jamie Allen to strike with power, but only into an Orient defender guarding his goal line.
Henderson hit the crossbar, though had been flagged for offside, before the break, with the goal-less scoreline suiting those with Spireites sensibilities.
Dale manager Keith Hill had clearly warmed the ears of his players at the break, the hosts coming out firing for the second period.
However, it was Orient's Nathan Clarke who nearly did Rochdale an almighty favour as he flicked on a set piece 50 minutes in that visiting 'keeper Alex Cisak had to save athletically.
Sadly for Spireites, the pressure told on 65 minutes when Henderson was well-placed in the box to finish off a slick attacking mood from ten yards and hand Rochdale the lead.
Going behind in a game they needed to win, Orient pushed further men forwards. However, it was Allen who should have increased Dale's cushion, fluffing his lines with just the 'keeper to beat and prodding yards wide from inside the box.
Rochdale were efficient if not overly impressive to hold on for their win and keep the play-off race alive until at least the weekend, when the Spireites have matters back in their own hands as they host Bristol City.