Blues suffered their first defeat of pre-season as they were beaten 3-0 by Championship side Millwall at Roots Hall.
Former Blue, Ryan Leonard, opened the scoring with a well-taken volley that was bettered by a superb scissor-kick effort from Ben Thompson, with Troy Parrott adding a third for the visitors.
This was Southend's toughest test of pre-season and it was a familiar face that put the Championship side in front early on as Ryan Leonard scored against his former club.
Jake Cooper’s long diagonal ball from the back was headed back across goal by Matt Smith and expertly volleyed first-time by Leonard from 12-yards out beyond Mark Oxley.
Blues responded well to the setback and carved out their first chance of the game when a loose ball inside the box fell to Terrell Egbri who curled his effort just wide.
But Southend then suffered a blow midway through the first-half as Harry Lennon limped off injured with just 20 minutes on the clock to be replaced by Miles Mitchell-Nelson.
Shortly after Ben Thompson's effort was parried clear by Oxley before Connor Mahoney tried his luck from distance seconds later to force another save.
Stephen Humphrys then stung the palms of Bartosz Bialkowski with a low drive that was well held by the Lions goalkeeper before Gary Rowett’s side made it two.
Jiri Skalak found space on the right to whip in a wicked cross towards Thompson who connected with a perfectly timed scissor-kick to find the bottom corner and put Millwall 2-0 up at the break.
As the rain came down at Roots Hall, Blues went close to halving the deficit right after the restart as Richard Taylor pushed forward only to drag his left-foot shot just wide of Bialkowski’s goal.
Millwall though would push on and extend their advantage before the hour mark as on-loan Tottenham striker Troy Parrott grabbed the Lions' third of the afternoon.
A neat through ball from Murray Wallace found the run of Parrott who had got goalside before lifting the ball over the advancing Oxley to add to Millwall’s lead.
The Spurs loanee then almost made it 4-0 after Mitchell-Nelson’s loose pass was picked off by Jed Wallace who played Parrott in only for the striker to hit the foot of Oxley’s post.
Molesley's side forced a string of corners as they tried to reduce the arrears and with a little under 15 minutes to go the Blues boss made eight changes with just Oxley and Taylor lasting the full 90.
Neither side would add to the scoreline in the remaining minutes as Millwall ran out 3-0 winners at Roots Hall, but it was a good test for Molesley's men who added to their fitness levels in the build-up to the start of the season.
Blues Starting XI: Oxley, Bwomono (Howard 77’), White (Osimeh 77’), Lennon (Mitchell Nelson 20’), Taylor, Egbri (Kinali 77’), Phillips (Hutchinson 77’), Klass (Gard 77’), Green (Trialist 77’), Humphrys (Kelman 77’), Goodship (Acquah 77’). Subs Not Used: Seaden
Millwall Starting XI: Bialkowski, Wallace, Hutchinson, Cooper, Thompson, Smith, Ferguson, Leonard, Bennett, Mahoney, Skalak. Subs: Sandford, Brown, Muller, Hunter, Tiensia, Malone, Williams, Wallace, Burey, Bradshaw, Parrott
Southend United: None
Millwall: Ryan Leonard 6’, Ben Thompson 35’, Troy Parrott 57’