Who's on the bag?

Read this story about Retief Goosen’s caddie.

Retief has his wife’s brother on the bag.
He has never played golf. Never caddied before. But he does what Retief wants, to shut up and keep up. Retief takes his own yardages and his caddie just carries the bag and rakes the bunkers.
That’s it. He has never told Retief anything and Retief has never asked him anything.
Retief was playing in The Masters this year and stood on the 6th tee and there was a large crowd standing behind them.

Retief all of a sudden asked his caddie if he thought it was a 5 or a 6 iron.
The caddie took out his cigarette, glanced at Retief and said:

and went back to watching the crowd…