The Scot, whose £8million gamble on the 19-goal striker has paid off in spectacular fashion, is lining up a fresh pay deal for the club's prized asset.
"To be just short of that - and you are talking about the two best players in the world - and the big guy has been scoring goals for us left, right and centre.
"Going to the World Cup is a major thing for any footballer. Belgium have one foot in it. If he did it again for us next season, then he's in a different place if he goes to the World Cup. If he does well there....
"But there is a risk. You think if you move somewhere it's going to be exactly the same and, basically, it's not.
"It's a gamble whenever you move. It may look great from the outside but if you are not in the right place at the right time, then you might not be able to kick on.
"But Christian is not a naive young kid. He's got his head screwed on."