The 26-year-old who has been out for 18-months has been unable to make the start of pre-season training where he had hoped to prove his fitness to manager Kenny Jackett.
"James is struggling in terms of his rehabilitation," said Jackett.
"We hoped he'd be fit for the start of training, but his leg will take longer. It's very difficult to prejudge, I need to talk to specialists and to James."
Elsewhere, the lastest on the payment of Bayo Akinfenwa to Torquay is to be negotiated by the clubs who hope to avoid going to tribunal.