Chesterfield are being held to a 1-1 draw in League One by bottom side Leyton Orient, after David Mooney cancelled out the Jay O'Shea penalty.
Leyton Orient's woes could be lifted as they are level 1-1 at half time against Chesterfield thanks to David Mooney cancelling out Jay O'Shea's penalty.
Chesterfield were the better side in the opening exchanges, their width provided by a 4-4-2 formation allowing debutant Mark Duffy to make instant inroads.
The Spireites took the lead on 18 minutes, when Caolan Lavery was pulled down while chasing Jimmy Ryan's pass. O'Shea quickly stepped up, and sent Orient keeper Alex Cisak the wrong way.
Orient looked sharper after the setback, and drew level when Chris Dagnall squared having broken the offside trap, allowing Mooney to stroke home from six yards out.
Result: Bent, Hughes fire Derby into fifth round >