Central defender Thomas, released by Southampton, signed a one-year deal on Tuesday and is expected to make his full debut in Rovers' first home league game of the season due to a long list of injuries that manager Sean O'Driscoll is having to contend with.
Skipper Brian Stock hopes to return after international duty with Wales and midfield partner Simon Gillett is available after missing the midweek Carling Cup defeat to Accrington through suspension.
But O'Driscoll was without midfielder James Coppinger (leg), Billy Sharp, James Hayter and Martin Woods (all groin) on Tuesday night, while John Oster and James Chambers both remain long-term absentees due to knee injuries.
