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."
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