Rochdale kept their play-off hopes alive with a 3-1 victory that pushed Rai Simons and his Chesterfield teammates closer to relegation.
The damage was done in the first half when Ian Henderson, Callum Camps and Jamie Allen put Rochdale in control and although Kristian Dennis replied early in the second, the visitors were never seriously threatened.
Simons came on at the break.
Nathaniel Mendez-Laing struck a post in the 14th minute before Keith Keane played Henderson through to finish with a chip over Thorsten Stuckmann two minutes later.
Rochdale dominated and scored twice in the space of two minutes before the interval to send home fans heading for the exits.
Camps found the bottom corner from 25 yards when a corner was half-cleared in the 40th minute and then put Allen in to score with a low shot across Stuckmann.
Chesterfield pulled one back through a 25-yard shot from Dennis in the 51st minute but the home side had David Faupala sent off in stoppage time for a late challenge on Joseph Rafferty.
Reggie Lambe and his Carlisle United teammates saw their winless run in Sky Bet League Two extend to seven games as Crewe secured a 2-0 victory at Brunton Park.
Carlisle United played with 10 men for most of the second half after Shaun Miller was sent off while goals from Callum Cooke and Jordan Bowery gave Crewe a third straight win.
Carlisle, without a goal in those seven games, started purposefully and Jamie Proctor, their on-loan Bolton striker, was denied an early goal by an offside flag.
However Alex took the lead in the 34th minute when George Cooper's ball into the box found Cooke running clear and he cleverly steered the ball past Mark Gillespie from close range.
Carlisle went down to 10 men in the 51st minute when Miller was shown a straight red card for a foul on Oliver Turton.
Crewe made it 2-0 in the 61st minute when Cooper skipped past Luke Joyce to get to the by-line and Bowery at the far post was left with an easy tap-in.
The visitors should have had another in the closing minutes when Cooke was through on his own only to be denied by Gillespie.