A frustrating night at Home Park saw Chesterfield overtaken at the top in League Two as they went down to John Sheridan’s Plymouth Argyle.
The Spireites enjoyed the bulk of possession but failed to turn their dominance, particularly in the second half, into goals.
Reuben Reid put Plymouth ahead during a first half in which he could have grabbed a hat-trick as he tormented the visitors’ defence.
Ritchie Humphreys pulled the Spireites level but their joy was short-lived as a fine solo effort from Reid gave the hosts all three points.
It moved Plymouth up into the play-off picture while Rochdale leapfrogged Chesterfield at the top after a 3-0 win at Northampton Town.
Paul Cook said: “We know there will be bumps and bruises along the way. It’s a promotion campaign that we’re on, it doesn’t mean we finish with promotion or finish in the play-offs, it means we must finish the season as strongly as possible.
“We’re very disappointed because in the second half we never felt like we were going to lose the game. We were in the ascendancy. It was a question of if we could score, when we could score, could we get the next one?”
It was a scrappy start as Plymouth, managed by Cook’s predecessor Sheridan, got men behind the ball and opted to attack swiftly on the break.
Reid and Lewis Allessandra looked to get in behind the Spireites at every opportunity, before the latter was replaced after picking up a knock.
Chesterfield, who were unchanged from the win over Oxford, needed to get hold of the ball and Jimmy Ryan soon took responsibility working in the middle of the park.
Gary Roberts had sight of goal from inside the area, when he was first to react to Jay O’Shea’s partially cleared cross, but the winger chose to take a touch with his right before looking to get a shot away and was crowded out.
Ollie Banks and Ryan tried their luck from range only for Jake Cole, in the Plymouth goal, to comfortably get his body behind both efforts.
Reid, who had already tested Tommy Lee’s handling from distance, gave the hosts the lead when he latched on to Alessandra’s header and shot across goal into the far corner of the net.
The former Rotherham United man could have had a second in as many minutes when he skipped inside Ian Evatt only to drag his shot wide of the mark.
Reid was a nuisance all evening and he had another sight of goal just before the interval which he blazed high over the bar from eight yards.
Chesterfield enjoyed much more of the possession and Richards showed his attacking prowess when he forced Cole into a smart save low to his left.
The visitors’ lone front man probably should have levelled moments later when he flicked Tendayi Darikwa’s cross onto the bar from two yards out.
Spireites kept the pressure on and, when the ball dropped to Humphreys 20 yards from goal, the defender smashed a low shot which took a deflection beyond Cole.
But within a minute Plymouth’s lead was restored.Reid evaded a couple of challenges and unleashed a powerful shot which flew beyond Lee into the bottom corner.
Substitute Dan Kearns caused their backline problems and Richards was twice marginally away from making contact to right wing crosses to pull Chesterfield level.
Lee was called into action once more to prevent former Spireite Neal Trotman’s glancing header while substitute Eoin Doyle forced a strong save from Cole.
There was still time for Lee to make another crucial stop to deny Conor Hourihane from close range.
Plymouth (3-5-2): Cole; Blanchard, Trotman, Nelson; Gurrieri, Young, Wotton, Hourihane, Parsons; Reid (Morgan 81), Alessandra (Obadeyi 35)
Spireites (4-2-3-1): Lee; Darikwa, Evatt (c), Cooper, Humphreys; Morsy, Ryan; O’Shea (Kearns 61), Banks (Bennett 61), Roberts (Doyle 69); Richards.
Goals: Reid 28, 58; Humphreys 57.