The former Barnet forward had to be substituted at half-time of their 2-2 draw with AFC Wimbledon on Saturday with a foot injury and the medical staff are nursing the Irishman ahead of kick-off.
Young striker Jamie Reid will hope to keep his place in the starting line-up after two goals on his first start for the club earned the Grecians a point against the Dons.
Another positive from that display was the return of Alan Gow for the first time since rupturing ankle ligaments back in February. The Scot is expected to be on the bench once more as he builds his match fitness.
Matt Oakley (shoulder) and Liam Sercombe (ankle) remain sidelined for the Grecians while Kevin Amankwaah had surgery on his ankle this week.
City, who have never beaten the Robins in their seven meetings, are a point off the play-off places and know that anything other than maximum points could see them miss out.