A DOMINANT display at home from promotion favourites Chesterfield brought 10-man Bury's brief winning run to an end.
But a harsh-looking straight red card for Shakers playmaker Danny Mayor on the stroke of half-time had a large bearing on the emphatic scoreline.
Wingers Gary Roberts and Jay O'Shea ran the Bury backline ragged from the word go and the pair combined for the opening goal in the 16th minute.
Shakers centre-back Nathan Cameron could not get a clean header on O'Shea's cross from the right, flicking the ball to Roberts who volleyed into the roof of the net at the back post.
The match became more and more heated as the half progressed, with referee Tony Harrington dishing out three yellow cards before giving Mayor his marching orders in the second minute of stoppage time.
The on-loan winger can think himself unlucky though - despite leaving his foot in with studs showing, there was no force or malice in the 22-year-old's tackle and Matty Brown's dramatic reaction did little to guide the referee in the right direction.
Cameron, who picked up his fifth booking of the season and, along with Mayor, will be suspended for next Saturday's match at home to Burton, was withdrawn at half time.
But, after putting on Tom Soares in an attacking switch, any hopes manager David Flitcroft harboured of getting back into the match were dashed when O'Shea rifled in Chesterfield's second with an unstoppable 25-yard shot.
Harington again took centre stage for the home side's third, overruling his asistant referee's offside flag, after Soares headed into his own net under pressure from Chesterfield striker Marc Richards.
And debutant Dan Gardner rounded off Bury's misery with four minutes remaining, coming off the bench to fire home the Spireites' fourth with a breakaway effort that looped in despite keeper Brian Jensen getting a strong hand to it.
The defeat saw Bury drop a place to 19th in the League Two table, just a point above the drop zone.