Manager Aaron Webster described Belper Town as Jekyll and Hyde as they went down 4-1 at 10-man Carlton Town.
The Nailers had drawn level at half-time, vut went down to their 15th Evostik South defeat of the season as two late goals ended the contest.
Joe Searson-Smithard made his Belper debut on loan from Notts County in place of Jack Livesey.
The home side took a 13th-minute lead when Mamoke Akaunu tapped in from close range.
Belper reacted well as Jack Hallahan curled a delightful free kick over the wall to immediately equalise.
Belper went on to edge the first period and Hallahan should have doubled his tally, but blazed over Alex Steadman’s cut back.
Compacting the midfield stifled the home side’s rhythm and limited any meaningful attacks.
Jake Carlisle slammed a header straight against the post to end a half that could have seen Webster’s men well in front.
Their good work quickly turned sour within the first five minutes of the restart.
Out of nothing, former Nailer Ben Hutchinson stroke home a powerful effort to restore The Millers’ advantage.
Belper lacked cohesion and rarely looked like drawing level for a second time.
Hutchinson hooked a pass over the Belper backline to Wilson running through, but new keeper Joe Searson-Smithard smothered his attempt.
Darol Lucas was dismissed for a second yellow card after a late challenge, but Carlton still stretched their lead.
Jordan Wilson drifted in on the left and placed his shot past the feet of the keeper with three minutes remaining.
Akaunu then bagged his brace and Carlton’s fourth, running straight through after winning possession at a Belper corner.
Belper Town: Searson-Smithard, Hunt, Goodard, Allen (Birks 67), Carlisle, Harrison, Steele (Jebbison 85), Lloyd, Steadman, Hallahan, Garnett (Browne 67).