Hanson has missed City's last two matches after being troubled for a number of weeks now with a back problem.
In an attempt to finally rid the striker of the injury, City have given Hanson time away from the action to rest and recoup after originally trying to nurse him through games.
With this in mind, Parkinson has told fans that Hanson will only be brought back into the fray when he is completely free of injury and back in top shape again.
Parkinson said: "With Hans (James Hanson), there is only a slight improvement for him so far.
"It is important for James and for ourselves that he is completely right the next time he goes out on the pitch.
"He wasn't 100% in the last two or three games that he has played for us and he hasn't really trained with us since the Brentford game.
"That sort of thing catches up with you after a while.
"We have to firstly get the injury right and then get him enough training under his belt to able him to play like we know James Hanson can play."
Nathan Doyle (groin) is also expected to miss out at the weekend, although there is hope that Adam Drury could be involved after making an earlier than expected return to training today (Thursday).
Parkinson said: "(Nathan) Doyley is still struggling a bit with his groin. He is slowly improving but it is taking a bit of time to get him right.
"We'll have to wait with Adam and see how he reacts tomorrow but he has trained today.
"It seems the injury wasn't as serious as we first thought."