Blues fell to a 2-0 defeat and ended the game with 10 men against Colchester United with goals from Michael Folivi and Harry Pell the difference at the JobServe Community Stadium.
After a quiet opening half an hour, an error from Mark Oxley was punished by the home side after Pell's effort was parried into the path of the onrushing Folivi who tapped home the opener.
A few minutes later and Pell doubled Colchester’s lead by smashing the ball in from inside the penalty area after Callum Harriott’s corner had fallen fortuitously for the U’s captain to put his side 2-0 in front before the break.
Southend were unable to muster a response in the second-half and ended the game with 10 men after a rash challenge from Jason Demetriou on Pell resulted in a straight red card being brandished by referee Kevin Johnson.
Defeat for Phil Brown’s side leaves them eight points adrift of Barrow and safety in League Two with just nine points left on offer from their final three games of the season, while Colchester’s second straight win has effectively guaranteed their safety.
In the lead up to the game, Blues boss Phil Brown had described the clash between the two Essex rivals as a must-win for his Southend side, knowing that defeat to the U’s could all but spell the end of Blues’ stay in the Football League with three games remaining.
And having put in a positive display against promotion-chasing Exeter on Saturday, Brown made just the one change to the side that drew 0-0 down in Devon with Brandon Goodship leading the line up-front in place of Simeon Akinola.
A handful of hours after Southend had drawn at St. James Park, Colchester picked up a vital three points at home to Walsall, so, unsurprisingly, Hayden Mullins named an unchanged Colchester starting line-up.
Unlike most of the 77 previous derby games between these two, this one took a while to get going with the first shot in anger at either end coming when Callum Harriott tested Mark Oxley with a low shot from the edge of the area.
Oxley dealt with that effort well but he was caught out moments later by another long-range effort as Colchester took the lead. This time, Harry Pell’s shot in the 30th minute was too hot to handle for the Blues number one and Michael Folivi profited to tap home.
It was a moment to forget for Blues, but there was little Oxley could do about the home side’s second seven minutes later. Harriott’s corner from the left fell perfectly for Pell to run onto and smash the ball in from inside the box.
Southend had a mountain to climb now if they were to pick up a result and they could have given themselves some hope going into the break if Jason Demetriou had found the target with his effort in first-half stoppage time which ended up being sliced harmlessly wide.
Despite showing some urgency after the interval, Blues could barely lay a glove on the home side in the second-half with the best they could muster a long-range effort from Reeco Hackett-Fairchild that wasn’t troubling Shamal George’s goal.
And things only went from bad to worse for the visitors as frustrations boiled over to the point where Demetriou’s rash challenge on Pell inside the centre-circle was immediately punished with a straight red by referee Kevin Johnson with 20 minutes remaining.
That was to be the final action of note on the night as Colchester happily played out time to secure a second straight win, while Blues know that anything less than a win against Leyton Orient on Saturday will spell the end of their stay in the Football League.
Colchester United XI: George, Welch-Hayes, Smith, Pell (C), Harriott, Chilvers, Eastman, Clampin, Wiredu, Folivi (Brown 54’), Nouble. Subs Not Used: Gerken, Lapslie, Sowunmi, Senior, Oteh, Stevenson
Blues XI: Oxley, Bwomono (Cordner 73’), Hobson, Goodship (K Taylor 46’), Hackett-Fairchild (Egbri 67’), Demetriou, Holmes (Acquah 83’), Walsh (Halford 46’), Hart, Ferguson, White. Subs Not Used: Seaden, Olayinka
Referee: Kevin Johnson
Assistants: Anthony Da Costa & Scott Williams
Fourth Official: Declan Bourne
Colchester United: Michael Folivi 30’, Harry Pell 37’
Southend United: None
Colchester United: Callum Harriott 49'
Southend United: John White 75’, Tyler Cordner 90+1', Greg Halford 90+3'
Colchester United: None
Southend United: Jason Demetriou 69’