Striker Millar was involved in a collision with team-mate Jose Baxter in the Capital One Cup defeat against Derby in midweek and is suffering from what the club termed a 'whiplash-type injury'.
Fellow forward Clarke-Harris had to come off in the clash with the Rams due to an ankle injury and he is rated as 50-50.
Should either player miss the contest, the door could be opened for summer signing Charlie MacDonald, who was an unused substitute on Tuesday.
- Sports & Recreation
- Disease & Medical Conditions
- Jose Baxter