http://cstpr.colorado.edu/prometheus/archives/climate_change/001169this_is_just_embaras.html

Regression to the mean

So I read Kahnemanns Thinking fast and slow and he claims golfers would try harder if they are close to being on par but not quite so hard when they are under par which would explain why par is the expected outcome for a professional golfer.
So why isn't that already explained by the regression to the mean?
Answers or links to answers very welcome.