McKenzie ruptured his Achillies against Birmingham City last season and is now out of contract.
"Injuries are always difficult because a lot of people don't see what it puts you through when you are trying to get fit again," said McKenzie to the CT.
"It's been a really massive individual battle to get myself back into training again but I've had ten days of full training now and it feels good to get back on the practice pitch.
"The gaffer understands what it is like because he's been there himself so we are both on the same page.
"But a lot of the responsibility to get fit falls on you as a person and sometimes it's easy to miss all the hard work you have to put in.
"You want to get back and that's why I've taken it upon myself to get help from the best specialists alongside everything the club are doing for me.
"Even though I'm training again now you still have to be careful.
"Eight months out is a long time and while you are running and kicking a ball again you are obviously not match-fit and niggles have a danger of creeping in.
"But I have confidence in my ability and I know if I can keep myself on the pitch I know I can do a job."