The striker went to see a specialist this week and received an injection which should help the healing process but the problem has still ruled him out for around seven days.
On-loan winger Danny Ward came off after 37 minutes of last weekend's 2-2 draw at Wycombe nursing a thigh problem but he returned to training towards the end of the week and should be okay.
Midfielder Jon-Paul McGovern and full-back Alan Sheehan have both been receiving treatment for muscle soreness but are fine and will start.
Callum Kennedy is now back to full fitness after a lengthy lay-off but whether he is handed a place among the substitutes remains to be seen.
The Robins are already assured of a top-six finish and still harbour hopes of closing the four-point gap on second-placed Leeds, although every point is important with home advantage in the play-offs up for grabs.