Alex McLeish has told striker Garry O'Connor he has to 'mature quickly' and prove he is good enough to be a first choice player at Birmingham.
New Blues boss McLeish knows all about O'Connor's finishing abilities from working with him when manager of Hibernian and then head coach of Scotland.
But he has seldom been able to break into the first eleven since moving from Lokomotiv Moscow to St Andrews in a £2.65 million deal last summer.
McLeish, whose side face Newcastle at St. James' Park on Saturday, said: 'Garry came into the Scotland set-up and did extremely well.
'He played in a friendly against Austria where he looked really composed. He looked like a centre-forward who knew what he was doing. Then against the Faroe Islands, he scored a precious goal for us.
'Maybe he lost a little bit of confidence with not starting for Birmingham too much - but now everyone here starts with a clean slate.
'Garry has got to prove he's good enough to be in the team and he's got to be better than the other players competing for the same place.'
McLeish, who brought O'Connor on as a substitute in the 3-2 win at Tottenham, added: 'Garry has got ability, there's no doubt about it. He can shoot with either foot, is decent in the air and is mobile.
'He's got all the attributes but it's up to the player himself to get it all together and to have the positive mind that he can pull it off.
'He's got to mature very quickly and he knows we won't accept anything other than what we see as what a professional footballer is all about.'
McLeish will encourage his players to play a passing game even though he accepts he does not have the massive funds needed to bring in the top quality exponents of that style of play.
He said: 'It is difficult to have a philosophy in football when you don't have the millions you would like to have at your disposal to bring the top class players in the world to play a beautiful passing game.
'But I have always encouraged my players to pass the ball - even with Scotland against France in Paris. We defended for quite a lot of the game but the boys showed great composure, belief and confidence.
'These lads here must do that. If these guys here have got into the Premiership they must have good ability and they must be able to take the ball and pass the ball.
'However I accept that sometimes you have got to find Row Z in the stand. There are philosophies and there are philosophies.'