Goals from Mooney and Barrett earn the three points for the Blues at the Den.
Headed goals from David Mooney and Adam Barrett saw Blues bounce back from defeat to record a 2-0 win over Millwall at The Den and register their first away win of the season.
There were five changes from the side that lost to a solitary goal at home to Shrewsbury Town last weekend, as Luke O’Neill, Cian Bolger, Luke Prosser, Gary Deegan and Joe Pigott came in to the starting line-up.
David Worrall had Blues’ first attempt of the game, firing a half-volley wide of goal before Southend won the first corner of the game in an encouraging opening ten minutes.
Captain for the afternoon, Michael Timlin, saw yellow for a foul on Shaun Williams, before Adam Barrett stood firm to prevent Aiden O’Brien from breaking clear on goal.
O’Brien then met a cross from Jimmy Abdou, but his headed effort on goal was easily dealt with by Blues keeper Dan Bentley.
Bentley was on form and showed his worth once again in the 33rd minute, rushing from his line to deny O’Brien in a one-on-one after the Millwall man capitalised on a quick throw-in.
David Mooney then headed Blues in front in the 37th minute, rising above the Millwall defence to glance a header past the reach of Lions’ stopper Jordan Archer, after a lifted cross from Worrall.
O’Brien continued to occupy promising positions in the final third, but blazed one effort over before sending a header wide of goal before the arrival of half-time.
Millwall looked to hit back at the start of the second half, but were stung when Blues defender Barrett rose to thump a header past Archer and into the back of the Lions’ net.
Despite finding the net, Barrett was injured in the process and promptly replaced by Glen Rea.
Ed Upson made way for the hosts, with former Blues forward and current Millwall boss Neil Harris sending on a third striker in the form of Lee Gregory.
Pigott went to ground in the penalty area after a push from Mark Beevers, but nothing was given by referee Mark Haywood, who allowed play to continue.
Ryan Leonard then took aim from range but failed to trouble Archer as Blues went in pursuit of a third goal.
As Millwall looked to find a way back into the game, Steve Morison headed just Bentley’s goal.
Harris made his final two changes with 23 minutes remaining, as Paris Cowan-Holl and Shane Ferguson entered the equation, with Fred Onyedinma and Beevers exiting.
Morison then found room in the area to unleash a powerful strike in the 71st minute, but Bentley was equal to it, punching the ball away from danger.
Deegan was shown a yellow card for a late challenge, as Millwall continue to press for a goal.
A low cross found O’Brien with space in the penalty area, but the Irishman’s prodded effort was kept out of the goal by another fine save from Bentley, diving low to his right.
Myles Weston replaced goalscorer Mooney, as Blues boss Phil Brown made his second change of the afternoon.
Bentley kept his clean sheet intact with just three minutes remaining, pulling off a low save to his left after a well-struck effort from Williams.
Millwall continued to threaten as the fourth official indicated a minimum of six additional minutes, but only managed to force one more save out of Bentley.
A dipping strike from O’Brien deflected, but the Southend keeper was still equal to it, back-pedalling before catching the ball.
Jason Williams then came on in added time, replacing Pigott.
Blues saw out the six minutes of additional time, claiming a first win on the road in this League 1 season.
Southend United: Bentley; O’Neill, Bolger, Barrett (Rea - 52’), Prosser; Worrall, Leonard, Deegan, Timlin; Mooney (Weston - 83’), Pigott (Williams - 90’).
Unused Substitutes: T. Smith, Atkinson, Wordsworth, Payne.
Attendance: 10,228 - including 1,097 from Southend