Midfielder Smith missed Tuesday night's 2-0 win over Portsmouth with a hamstring injury and striker Helguson has been sidelined for the last two matches with a groin strain.
Hogan Ephraim and Ishmael Miller are likely to keep their places if Smith and Helguson are ruled out again.
Hungarian midfielder Akos Buzsaky is still unavailable following knee surgery but he is back in training and could be back in contention in a couple of weeks.
Defender Peter Ramage is still on the sidelines following a cruciate injury and strikers Jamie Mackie and Patrick Agyemang are continuing their recovery from broken legs.
Source: PA
Source: PA