Barker and Phillips both missed Saturday's 1-1 draw at Accrington with respective calf and toe injuries.
And manager Paul Sturrock's defensive dilemma deepened when centre-back Cresswell was given his marching orders shortly after the hour mark, meaning he now starts a three-match ban.
The Scot, already without leading scorer Gavin Tomlin (thigh) and midfielder Michael Timlin (broken leg), is also sweating over further bumps and bruises among his squad.
Elliot Benyon on Monday rejoined Torquay on a one-month loan deal and so will not be involved.
The seventh-placed Shrimpers go in the clash just two points and two places behind Cheltenham in the table.