Phil Brown says Tuesday's Essex Derby away against Colchester United is the biggest game in the club’s history.
After results at the weekend, and the U’s moving six points clear of Blues from the relegation zone, the Southend manager is under no illusions what this game means.
Brown said his side must show they want it more than the opposition, and he will select his team with that in mind.
"In our history, it’s going to be the biggest challenge and the biggest game," said Brown.
"The game on Saturday wasn’t the result that we were looking for so Colchester have put a bit of space between us again.
"I’m going to say it, regardless of whether you’re going to ask the question about a must-win situation, it is a must-win situation.
"We’re going into that in the full knowledge that we must win four games.
"If we can get to 50 points it brings a whole new scenario to the ballpark. I’m not convinced everyone above us in the 40’s are safe, but they might be in a better situation than we are that’s for sure, so psychologically they’re going into games thinking if they win they might be safe. Bottom line is, we need to win this game or it could be the end of a great era.
"We’ve spoken about it. We came in on Sunday, we prepared for the game straight away after the Exeter draw and straight into a training session with the players that didn’t play, and the others did a warm down session.
"I got to grips with them straight away and I was buoyed by the performance on Saturday.
"The players were very committed [on Saturday], very focussed and yes we did finish on the back foot a little bit but it was to be expected because they [Exeter] are fighting for something.
"The word fight is something that has to be on show tomorrow night. We just have to show that we want it more than Colchester. That’s the only way we’re going to win the game of football.
“They’ve got equally as much talent as we’ve got, they’ve got equally as much physique and height, set-pieces and all those small things that go into a big melting pot to win a game of football.
“We’ve got to show our supporters that we want it more than them and I’ve got to put a team out that’s going to show that.”