Fettis suffered a knee injury at Oxford on Saturday, and will miss the bank holiday double-header this weekend, starting with Cheltenham at the KC Stadium tomorrow.
Musselwhite will start in goal, and as Peter Taylor doesn't look like bringing in a backup keeper on loan, 17-year-old Danny Harvey is expected to be drafted into the squad. Harvey has twice been on the bench before, and has also made a handful of appearance for the reserves after a year on YTS terms.
Taylor is unlikely to make any further changes, with Richie Appleby, Andy Dawson, John Anderson and Ryan Williams all missing once again.
Expected line-up (4-4-2): Musselwhite; Thelwell, Hinds, Joseph, Delaney; Price, Green, Ashbee, Elliott; Burgess, Allsopp.
Subs: Harvey, Whittle, Melton, Keates, Forrester.
Don't forget to make your Beat The Manager prediction for this match - click here to play.