Millwall maintained their unbeaten start to the season with a hard-fought draw in a physical Roots Hall encounter.
Both The Lions and Shrimpers defences came out on top in an absorbing battle in which the two teams could not be faulted for their effort or commitment.
Den boss Kenny Jackett again changed his starting line-up from the team that kicked off Tuesday's game with Oldham with Marc Laird and Jason Price replacing Chris Hackett and Steve Morison in a 4-3-3 formation.
The Lions went into action on the back of an unbeaten run stretching back to the start of pre-season - but The Shrimpers were always going to prove a tough test following a solid start to the season themselves.
Millwall, wearing an all-white away strip following a delay by the suppliers with the new red and black kit, were left feeling somewhat black and blue following a bruising encounter.
And no individual felt that more than right-back Jack Smith, who played on nursing his right shoulder after virtually somersaulting over the terrace wall in the opening five minutes and landing awkwardly.
To his credit Smith battled on, as did his team-mates in a physical, fiery match played at a high-tempo.
Such was the frenetic pace during the opening 45 minutes that scoring chances were limited. Millwall carved out the first opening on seven minutes when Andy Frampton slipped the ball through to Laird, he in turn picked out Price on the right, but the striker opted to cross instead of having a shot at goal himself and the ball was comfortably collected by keeper Steve Mildenhall.
At the other end Lions keeper David Forde was forced into action with a smart stop after 15 minutes to push Lee Barnard's angled snap-shot over for the first of eight Shrimpers corners.
Forde came to the rescue again just past the half-hour mark, sp;rinting out of his area to thwart the danger after Anthony Grant had been put clear through from a fine diagonal Alan McCormack delivery.
Millwall brought on Neil Harris at the break and within seconds Chopper nearly marked his introduction in spectacular fashion, sending a diving header from Laird's cross inches wide of the post.
Chris Hackett entered the fray just before the hour mark as The Lions switched to a 4-4-2 formation, and with Southend showing greater enterprise going forward too, the game opened up nicely.
Alexander saw his 61st-minute strike smack the woodwork after Hackett's floating free-kick had caught the home defence napping whilst Southend were also denied by the woodwork when sub Alex Revell's low drive 11 minutes later crashed against the foot of the post.
It took a perfectly timed tackle by Tony Craig to deny Revell as he shaped to shoot from four yards and then Hackett wasted a glorious opportunity, volleying wide after Harris had picked him out unmarked inside the danger zone.
Alexander then saw his effort blocked on the line by Moussa, but with neither side able to find that vital killer touch, and both defences dominant, a draw was just about the fairest result.
Southend United: Mildenhall, Francis, White, Christophe, Heath, Barrett, Grant, McCormack, Barnard, Moussa, Freedman (Revell, 65mins). Subs not used: Walker, Sankofa, M'Voto, Betsy, Joyce, Sawyer.
Bookings: Grant (86mins), McCormack (90mins)
Millwall: Forde, Smith, Friend, Bolder, Frampton, Craig, Laird (Hackett, 59mins), Fuseini, Price (Harris, 46mins), Alexander, Martin. Subs not used: Sullivan, Dunne Barron, Grimes.
Bookings: Martin (37mins), Friend (43mins), Laird (52mins), Alexander (76mins), Smith (90+2mins)
Ref: Dean Whitehead