Town's head of sports science Dave Williams says the Blues will not rush Owen Garvan back from his illness. The Irishman developed post-viral syndrome in the wake of the bout of shingles which saw him miss most of pre-season.
Williams told the club site: "What Owen has is something similar to glandular fever and it effects your immune system.
"It's a problem that has followed the shingles and kicks in when you are feeling run down.
"Highly trained sportsmen and women are more at risk of illness than the average man in the street because their bodies are pushed to the limit over and over again. It runs their immune system down.
"With this sort of illness, it's imperative that you take the recovery period one step at a time and don't rush back too soon.
"We are doing one or two things to help him on his way, but the simple truth is he will be back playing football again when he is ready and no date has been discussed when that will happen.
"We have to take his recovery at the appropriate speed. He is back around the training ground but he's not able to exercise with any intensity at the moment. It's a case of waiting until his body sorts itself out."
Garvan said earlier this week that the illness had at times left him too weak to get out of bed on his own, but that he was showing signs of recovery.