Southend's triumph was marred by a broken leg suffered by Martin Taylor, the Derby goalkeeper, after a collision with Regis. Until then, Derby had looked the more enterprising outfit and should have taken the lead early on.
Dean Sturridge headed wide from a Gordon Cowans free-kick in the ninth minute and was later guilty of the miss of the match when he blazed high and wide from six yards.
Bolton took an early lead against Oldham with two first-half goals from Mixu Paatelainen and David Lee. However, Oldham's substitute, Paul Bernard, pulled a goal back in the 64th minute before Sean McCarthy grabbed the equaliser from close-range.
Sheffield United's hopes for a swift return to the Premiership took a knock when they were held to a 0-0 home draw by Barnsley.