The centre-half made his comeback from injury for the under-21s in the 2-0 defeat of Ipswich Town at St. Andrew's on Monday.
Morrison has been out of action since Blues draw at Sheffield Wednesday at the end of January.
"I am good to go now," said Morrison. "I have trained for the last ten days, played on Monday night, so I've ticked all the boxes now.
"It's just a case of training hard, trying to get back into the team and seeing where we go from there.
"There were no problems with the rehab, it was six to eight weeks initially, and that's what it's turned out to be.
"I feel fit now, which is the main thing. It's then a case of training and it will just be a case of what the gaffer wants to do.
"We've got two games in a short space of time, the whole squad will be needed for that, and I'm available."
Morrison travelled with the first team to Cardiff City on Saturday but didn't make the final 18.
Rob Kiernan and Jonathan Spector have been holding sway at the heart of Blues defence.
That pair have performed together well enough to keep captain Paul Robinson on the sidelines.
"There are two good defenders who are playing ahead of me at the moment," noted Morrison.
"We kept a couple of clean sheets through that good period. The lads have done really well.
"Rob's come in and done a really good job, I have been really impressed with him, and Specs has come back into the team.
"Rob has played really well, he's comfortable on both feet, he's aggressive, he's tall, he's been a good asset to the football club so far.
"I am not sure what the plans are for the future, but certainly I think he will be happy with how he has started here."
Morrison has missed 11 Blues games.
"It's been frustrating watching, especially when we had that little slip of form," he confessed.
"But we seem to have picked up. Obviously the weekend wasn't a good result, but before that it was four games without losing.
"The lads are making strides and we look quite comfortable in the table now, which is good."