Adam Scott of Australia makes a birdie putt on the 18th hole during the final round of the 2013 Masters Tournament at Augusta National Golf Club on April 14, 2013 in Augusta, Ga. - 

They don't get much attention, but the rules in sports matter. Think about the designated hitter in baseball -- more than 40 years later, people still grumble about the beefy sluggers. This week, golf's ruling bodies agreed to ban what's known as the belly putter, saying it helps keep the game pure.

And that's the trick for sports, how to tweak the game just enough to increase popularity without turning off hardcore fans. University of Chicago economist Allen Sanderson says a good example is when the Brooklyn Dodgers signed Jackie Robinson.

“It was chancy. It was the right thing to do. It was the moral thing to do and everything else, but there was some risk attached to that,” he says.

Sanderson says team owners were gambling white audiences would pay to see non-white athletes compete. Generally, sports owners are in business to make money. Rule changes tend to be more modest than breaking the color line, however.

Holy Cross economics professor Victor Matheson says usually sports focus on adding some razzle-dazzle. “We’ve seen lots of rule changes in the NBA and the NFL and hockey all designed to encourage more offense. More scoring,” he says.

But there’s a limit. Take baseball. Performance enhancing drugs helped drive the infamous homerun races between Barry Bonds, Mark McGuire and Sammy Sosa.

But University of Chicago’s Allen Sanderson says customers balked.

“At some point fans just said enough is enough. It’s just too artificial,” he says.

Sports economists think professional football is the biggest sports rule riddle out there today. The NFL must figure out how to protect its players.

Right now, it’s not clear how to do that. Prof. Matheson at Holy Cross says to understand what’s at stake look at boxing.

“There was essentially no way to take the brutality out of boxing. And boxing went from being the most glorified sport in the country, down to a sport that essentially no one watches anymore,” says Matheson.

Matheson says if the NFL doesn’t figure out how to adjust its game, the nearly $10 billion in revenue it took in last year could be in jeopardy.

Follow Dan Gorenstein at @dmgorenstein