Ryan Hall - suspended for Saturday's league opener against Stockport - is back in contention but a virus means he is likely to start on the bench.
Summer signings Bilel Mohsni and Adam Bouzid are not expected to feature again with the Shrimpers still waiting for their international clearance.
United chief Sturrock is keen to earn a result against the Robins but has said he will give his fringe players a run out.
He told the club's official website: "We want to be as competitive as possible and hope we can get a result to keep ourselves good financially. The League Cup can be a money spinner.
"I'm going to give several of my other players an opportunity tomorrow because I really have to have a look at people and get people up to match fitness."