Miller was set to be replaced by Ellis Barkworth after 15 minutes of the charity match before the defender received the ball and fell to the floor in serious discomfort.
After being helped into the changing rooms and to hospital the initial assessment is that the defender has torn his calf and is likely to be missing for 6-8 weeks.
"Gutted to pick up the injury" Miller said on social media.
"I'm determined to be back sooner than the initial diagnosis. It was only Tuesday at training I was saying how fit I felt but unfortunately that's football. Roll on the rehab!"
We would like to wish Paddy a speedy recovery! #ATAW
Updated 10:36 - 10 Aug 2018 by Jay Taylor