Ian Henderson scored the only goal as Rochdale inflicted a fourth-straight League One defeat on Chesterfield.
In a first half of few chances, Peter Vincenti headed over for the hosts while the Spireites saw Gary Roberts' effort saved by Josh Lillis.
Dale went ahead when Michael Rose's free-kick found Henderson, who touched the ball under keeper Tommy Lee.
Caolan Lavery went close to finding an equaliser in added time but Lillis produced a fine stop.
Chesterfield dropped to 10th in the table but are only three points off the play-off places, while Rochdale are a point behind in 13th.
Rochdale manager Keith Hill told BBC Radio Manchester:
Hill on Rochdale v Chesterfield
"Some of the younger players and some of the older players, have run out of steam mentally.
"It happens to promoted sides, whether it's a Premier League or League One.
"It's very difficult maintaining the standard and you do sometimes get bad performances.
"At this time of the season, more so than any other time, it's about results."
Chesterfield manager Paul Cook told BBC Radio Sheffield:
Cook on Rochdale v Chesterfield
"We didn't come under any great pressure today, it was a bit of a flat game.
"I actually felt first half we looked the better side. I felt we could go on and win but we're just not penetrating in that box.
"Whatever we're offering up at the minute doesn't seem to be enough."
- Published20 June 2016
- Published7 June 2019
