Match gallery: Carlisle United 2 Chesterfield 0
Chesterfield's relegation worries increased at Carlisle, as Jack Lester's side crashed to their 20th league defeat of the season.
Kelvin Etuhu opened the scoring and substitute John O’Sullivan sealed victory late on after Louis Reed had a goal disallowed for the Spireites.
Defeat means Chesterfield are now five points from safety in the League Two drop zone.