Fenton has been sidelined in recent weeks with a calf problem and will once again be unable to bolster the Shrimps backline.
It is an option boss Jim Bentley would have welcomed after branding the 1-0 Easter Monday defeat to Wycombe as the worst display during his time at the club.
"I'm still reeling a bit from Monday because we were so poor," he told Morecambe's official website.
"The pitch didn't help but we can't use that as an excuse because we were second best in far too many areas. I felt sorry for the fans because that just wasn't us and they deserve better than that.
"Rotherham will be really tough opponents but we have done pretty well at home against the top teams and I want us to show that same type of form and spirit this weekend."
Andy Parrish offers an alternative defensive option having come through a midweek reserve game on his return from a thigh injury.
Regular number one Barry Roche is expected to return between the posts after being rested in favour of understudy Andreas Arestidou last time out.