Shane Nicholson played 20 minutes in his testimonial return but was unable to help his Spireites side to victory as they lost 2-1 to neighbours Derby County.
After Nicholson had come through for a guard of honour ahead of the start, Ched Evans came close to giving the hosts a flying start when he headed Dan Jones's cross over the bar.
Derby were closer after 11 minutes when Max Lowe connected sweetly with a shot in the box and with Ryan Fulton beaten the ball bounced down close to, but not over, the line before being cleared by the Spireites defence.
The visiting attackers were showing their class with some crisp one-touch forward play, though Chesterfield too were threatening and Evans tested Jonathan Mitchell's handling with a powerful drive from well outside the box.
After Evans had seen a venomous freekick blocked, Ian Evatt went closest yet as he connected with O'Shea's corner but saw his header beat the 'keeper but not the Rams man covering the post.
The Spireites were growing into the game and providing an attacking threat, Evans fed Ariyibi on the right and the winger's excellent cross just evaded Jones who was rushing in to meet it.
Chesterfield were the better side by half time, Evatt again went close with a header from a corner, but this time his downward effort landed a foot wide of the post.
Following the interval O'Shea played neatly through for Evans into the box, the striker able to take a low first time shot, though substitute 'keeper Roos was able to save.
With Chesterfield unable to go ahead themselves, the visitors soon had the lead after 52 minutes when Jeff Hendrick's low shot deflected directly to Bent who had the simple task of finishing in the area.
However, the lead lasted just moments as on 57 minutes O'Shea finally bagged his goal after making room cleverly in the box and turning to sweep home a low effort at the near post.
The pendulum began to swing back into Derby's favour and Fulton had to be at his very best to make a spider-like save to keep out Bent's shot.
The Rams made an attack count midway through the half when substitute Rawson rose to head a corner into the top of the net and restore Derby's lead.
The Spireites needed a spark - and turned to a 46-year-old and man of the hour, as after 72 minutes Nicholson came on for Jones and took up his familar left-back position for the Spireites.
Evatt saw another header go close before substitute Kristian Dennis had a close-range shot blocked behind.
Johnny Russell forced a late Fulton save, but Derby had their win in a competitive encounter at the Proact.
Chesterfield: Fulton (gk) - Jones (Nicholson 72'), Raglan, Evatt, McGinn - Gardner (Morrison 75'), Liddle, Dimaio, Ariyibi (Graham 79') - O'Shea (Mitchell 75'), Evans (Dennis 75')
Chesterfield: O'Shea 57'
Derby County: Bent 53', Rawson 66'