The 20-year old West Ham United young gun spent last season at St Andrews to develop his game and it has paid dividends with some impressive performances already in the Premier League with the Hammers this campaign.
Clark told talkSPORT that Birmingham didn't really do much from a football perspective but helped the former Manchester United starlet with the mental side of becoming a better player.
"I didn't do anything on the football side, he's an unbelievably talented young man," Clark said of Morrison who has scored four goals so far this term.
"I basically told him it was all about the full package, what he was doing off the pitch as well as on it.
"It's about behaving in the right way, having a good attitude and that if you have discipline off the field it becomes second nature on the field.
"West Ham have been absolutely delighted with his response since coming back, he hasn't given them a moments problem.
"It was never about his attitude on the pitch or his work ethic, he loves the game and he was one of the fittest players at our club.
"He's got his first call-up to England's Under-21's this week, so if he can continue in the same vain and perform at that level, I think England will start to consider him, he can change a game in a flash.
"He was unplayable at times for us, he can go as far as he wants to go."
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