Ched Evans hit a hat-trick as Sheffield United beat Chesterfield to leapfrog rivals Sheffield Wednesday into the automatic League One promotion places.
Lee Williamson's volley from inside the box gave the hosts the lead before Franck Moussa levelled from long range.
Evans netted a penalty three minutes after the break and then completed his hat-trick within 20 minutes with a sidefoot finish and a near-post strike.
Chesterfield, who won the Johnstone's Paint Trophy on Sunday, remain bottom.
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Sheffield United manager Danny Wilson tells BBC Radio Sheffield:
"I thought there were some tremendous performances out there, but obviously when you score a hat-trick you're going to be flavour of the month.
"He (Ched Evans) is unplayable at times and you'd hate to be a defender against him in this type of mood.
"He's got a trick in his locker, he's got pace, power and he can hold people off, but he can finish."
Chesterfield manager John Sheridan tells BBC Radio Sheffield:
"I thought we did really well first half, I thought we were right in the game.
"The penalty is an absolute disgrace, it is a penalty, but it is a disgrace what we have done.
"The comedy of errors is unbelievable.
"You need leaders on the pitch and unfortunately we didn't have them at that time and it's been a big problem throughout the season."