The 25-year-old defender started in Saturday's 2-1 defeat at the hands of Hartlepool despite doubts over a head injury, but only lasted 64 minutes.
Liam Sercombe could be set for a recall if Duffy is deemed unfit.
Defender Rob Edwards and striker Richard Logan are both pushing for recalls after replacing Billy Jones and John O'Flynn at half-time against Pools, while Daniel Nardiello is also pushing for a recall after a 25 minute substitute appearance.
Arsenal academy graduate James Dunne looks likely to continue in midfield after playing the whole game despite concerns over a badly bruised leg.
The Grecians currently sit 15th in npower League One and will be looking to return to winning ways following their first defeat in five league games at the weekend.
Source: PA
Source: PA