Samuel Saiz fired Leeds ahead in the fourth minute but his shot needed a wicked deflection to beat Robins keeper Frank Fielding.
That inspired the Whites to a 3-0 win at Ashton Gate to end a three-game losing streak.
Thomas Christiansen shuffled his pack in a bid to kickstart their campaign.
And Southend gaffer Phil Brown, speaking on Football on 5: The Championship, believes Christiansen got the reaction he wanted from his players.
Brown said: “If you look at the size of football clubs in the Championship, it’s got to be close. Leeds would be up their with the biggest.
“They’ve just gone three straight defeats and they were desperate for this [win].
“He’s called upon it by the sounds of it and he’s got a response.
“That first goal was so important and they got a bit of luck there.”
When asked how important the first goal was, Brown said: “Absolutely, it turns everybody’s attentions to what you know your team’s capable of.
“You get on the front foot, you start pressing from the front, you start getting the ball back in the opposition’s half instead of dropping back and protecting what you haven’t really got. You’re hanging on to a point before you even start.”
Meanwhile, Christiansen hasn’t spoken to Pontus Jansson about axing him from his starting XI.