And he admits that, as well as keeping things shored up at the back, having scored four times from set pieces for Yeovil last season, more of the same will be expected of him with Blues.
"I scored a few headed goals," he added, "including the one that won Yeovil promotion at Wembley.
"And, with Nikola Zigic here too, I would imagine that if we're not scoring goals, there'll be some questions asked."
Green, who turned down the offer of a new contract at Mansfield, finished last season as Blue Square Bet Premier top scorer, with 26 goals.
"I'm over the moon," he told BBC WM. "It's a great opportunity for me."
The Welshman has played in the Championship before, having made six substitute appearances for Cardiff City after being signed by Dave Jones the day before his 20th birthday in early 2007.
"When I was at Cardiff maybe I wasn't old enough," he said. "But this is another chance to express myself at a higher level.
"I just want to play as many games as I can. I scored a lot of goals for Mansfield last season, a lot of them winning goals. And, if I can have half that success with Birmingham I'll be very grateful."
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