Gavin Tomlin's late winner saw Southend end a run of three league defeats with a narrow victory at Chesterfield.
In a lacklustre first half, Spireites striker Marc Richards almost broke the deadlock when he struck the bar.
Soon after Richards' powerful strike forced Shrimpers keeper Paul Smith into a smart stop.
The visitors created little throughout the match but claimed all three points when Michael Timlin sent Tomlin clear, who slotted home.
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Chesterfield manager Paul Cook told BBC Radio Sheffield:
"The level of performance, in my opinion, wasn't great. You've got you move the ball quickly, you've got to get round the back of teams who defend, and you have to put quality in the box.
"I don't mind saying that we want a well-balanced team at the club that can go right to left and put quality in the box.
"Our lads tried their best today and I have to problem with that. Unfortunately our willingness to try and win the game cost us."
Southend United manager Paul Sturrock told BBC Essex:
"I didn't think we played well today. I thought in the second half we worked very, very hard and got in the right areas a couple of times.
"But generally we were sloppy with our passing. A draw would have been a fair result.
"To be fair, there's been games where we've been away from home and deserved much more than we've actually got. It's swings and roundabouts.
"I'm delighted with the attitude of the players, the work-rate was immense and our shape was better in the second half."
Chesterfield 01 Lee 03 Smith 05 Trotman (Gnanduillet - 87' ) 06 Hird 12 Darwikwa (Lester - 64' ) 31 Cooper 08 Togwell 10 Whitaker (Townsend - 80' ) 15 Clay 34 O'Shea 09 Richards Substitutes 40 Barrington 17 Brindley 33 Townsend 23 Randall 14 Lester 21 Gnanduillet 22 Wafula Southend United 01 Smith 02 Clohessy 04 Spillane 06 Cresswell 15 Phillips 18 Leonard 23 Barker 08 Timlin 14 Hurst 10 Corr 21 Tomlin Booked Substitutes 17 Bentley 03 Straker 16 Prosser 19 Spicer 30 Woodyard 09 Harris 32 Njie
Ref: Mark Heywood