The Spireites went down to a narrow 2-1 defeat at home to Sheffield United after taking the lead when new recruit Chris O'Grady marked his first appearance at the Proact for Chesterfield with a goal.
Chris Wilder's men hit back with goals from Jack O'Connell and David Brooks to claim the win.
Five summer signings were named in the starting line-up. O’Grady partnered Delial Brewster in attack while Joe Anyon was in goal, with Scott Wiseman and Bradley Barry also featuring.
The visitors posed an early threat with Kieron Freeman having a goal-bound shot blocked following a corner.
For the Spireites, Brewster laid the ball off to Connor Dimaio, who was fouled. Dimaio’s free-kick over the defensive wall was gathered by keeper Simon Moore.
The breakthrough goal came just after the half-hour mark when Charlie Wakefield slipped a great ball through to Brewster who held the ball up well on the left-hand side of the area and squared to O’Grady (32) who tapped in.
There was a good chance for the visitors when O’Connell headed wide at the far post after meeting a Fleck corner.
United made a promising start to the second half with Samir Carruthers having a shot deflected wide and John Fleck seeing his effort saved by Anyon.
In the 56th minute, Gary Caldwell made his first change with Jak McCourt coming on to make his first appearance for Chesterfield at the Proact. He took over from Wakefield, who was warmly applauded as he left the field following an impressive display.
A double substitution followed in the 63rd minute when two other new recruits, Gozie Ugwu and Louis Reed, came on in place of Barry and O’Grady.
Just a minute later, Ugwu went desperately close to putting the Spireites further ahead. Finding himself through on goal following a defensive lapse, he looked certain to score after rounding Moore, but his effort came back off a post.
Brewster then had a shot blocked before the visitors equalised.
The goal came in the 72nd minute when O’Connell beat Anyon with a low drive from distance.
McCourt threatened to equalise late on with a rasping effort which struck the bar.
Brooks scored an 85th minute winner, making a surging run at the defence before producing a fine finish, firing low past Anyon.
Chesterfield: Anyon, Wiseman, Hird, Maguire, Evatt, Barry (Ugwu), Donohue (Mitchell), Dimaio, Wakefield (McCourt), Brewster (German), O’Grady (Reed).
Sheff Utd: Moore, Stevens (Lafferty), O’Connell, Freeman, Stearman (Wright), Basham, Coutts, Fleck, Carruthers (Thomas), Sharp (Lavery), Clarke (Brooks).