Tom Naylor’s first-half goal saw the Spireites beat League One leaders Portsmouth in the Emirates FA Cup.
Paul Cook made five changes from the side that beat Kidderminster as Harry Tyrer, Ash Palmer, Branden Horton, Darren Oldaker, and Michael Jacobs came into the starting XI.
Paddy Lane had Pompey’s first shot of the game from the edge of the box, but Harry Tyrer tipped the ball over the bar.
Ollie Banks came close for the Spireites after receiving a pull-back on the edge of the box from Will Grigg, but Banks’ effort was parried away by Will Norris.
Banks again came agonisingly close to putting the Spireites in front with a curling effort from the edge of the box that went narrowly wide.
Lane forced a good save from Tyrer with a near-post effort from the right-hand side.
The all-important goal came in the 32nd minute when the ball was crossed in by Darren Oldaker, following a free kick, and Naylor rose the highest to head the ball in.
Pompey had a chance when the ball was crossed into the back post and met by Colby Bishop, whose headed shot was well saved by Tyrer.
The Spireites came close at the start of the second half through Michael Jacobs. Jacobs cut in from the right-hand side and managed to get a shot away, but his effort was deflected wide for a corner.
Pompey came close, following a corner, and the ball fell to Abu Kamara at the back post, who tried to direct his header towards goal, but his effort went wide.
Some fans thought that they had doubled their lead when Ryan Colclough drove down the left-hand side and struck the ball into the side netting.
Substitute James Berry forced a good save from Norris shortly after coming on, with a powerful shot to the keeper’s near post.
After this impressive victory, attention will now turn to next Saturday’s home fixture against Barnet.
Spireites: Tyrer, Mandeville (Sheckleford 81’), Palmer, Grimes ©, Horton (Freckleton 71’), Oldaker (Berry 81’), Naylor, Jacobs, Banks (Colclough 64’), Dobra (Jones 71’), Grigg
Subs: Boot, King, Cook, Curtis
Attendance: 8,377 (1,566 away)
