The Northern Ireland international was on the bench for the opening game of the season against Manchester United but suffered a back problem shortly after and has been sidelined ever since.
But Johnson is now determined to make an impact on the Blues' season.
"I picked up a little niggle after the United game. So I had an injection a couple of weeks ago and I've been easing myself back in training," Johnson told the Birmingham Mail.
"It was nice to get out there. I trained a couple of days last week then played, so that was good.
"The result wasn't the best but it was just to be good out there.
"I feel OK, all right. It has just been frustrating so far this season for me," added Johnson.
"Unless I'm fully fit and training every day, I can't complain. I haven't been doing that. Once that happens, I get some sessions under my belt, hopefully everything else will take care of itself and I will get some first-team games, wherever it may be.
"I always want to be involved here. But, to be honest, there's not a lot you can do when you're not training every day and you're not available.
"And of course, there's a lot of midfielders here. That's the way it has to be. There's a lot of competition.
"You need a big squad, there's no doubt about it, and all the lads will probably be needed a various stages.
"But at the minute, I've not been much use to anyone."
Johnson could be loaned out if he is unable to force his way into McLeish's plans but the 30-year-old has not thought about that just yet.
"It's not really something I've given much thought to because I haven't been fit enough to play," he said.
"If I'm training over an extended period of time... I haven't really thought too far down the line. We will just see how it goes."