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Jim Brown averaged 5.22 yards per carry during his career, which helped him become the only back in history to average more than 100 yards per game. That's just one of our list of possibly unbreakable records in sports.

A volley winner, and it was over. After a handshake with his beaten rival, Andre Agassi, the singles king Pete Sampras kissed his wife, the actress Bridgette Wilson, who was pregnant with the first of the couple's two children. Sampras had cause to celebrate after what would be his final professional match: He had just added to his record with a 14th Grand Slam men's singles title at the 2002 U.S. Open.

Many observers assumed his remarkable record could stand for some time — or, at the very least, until his unborn child was in high school. Certainly, no one was worried about a swift and serious challenge from some upstart from Switzerland, who was a full 14 Slams behind.

On Sunday, Sampras and Wilson were courtside to watch Roger Federer win Wimbledon, the latter's 15th Grand Slam singles title. Their first child, Christian Charles? He's not even 7 years old.

"I have to give it him," Sampras said of Federer, after giving him the thumbs-up. "He's the best in my book."

And the record book, for many sports fans, is what matters most. That's how many measure greatness between athletes who play the same sport, but might not have played that sport in competition with each other, or perhaps not while each was in his or her prime.

Sampras and Federer faced each other only once, and Federer won, but the former was falling while the latter was rising. Margaret Court never faced Steffi Graf, who gave a spirited run at Court's record of 24 Grand Slam women's titles before falling two short, or active leader Serena Williams, who still trails by 13 even after her latest Wimbledon victory. Often, the grandeur of the record itself is measured by the length of time it endures. Court's has been the standard in women's tennis since 1973, though nothing compared to a baseball record that was broken in 2004, when Ichiro Suzuki broke George Sisler's 84-year-old single-season hits record with his 258th, followed by a 259th.

Jack Nicklaus won his 18th and final Grand Slam at the Masters in 1986, but most assume his reign over the most significant record in men's golf will end at roughly a quarter-century, with the hard-charging Tiger Woods only four behind. Nicklaus can't do anything now to make Woods' pursuit more difficult. Federer, however, still has good years in him, and he'll need to excel to hold off Rafael Nadal, who has already won six Grand Slams and might have won a seventh if an injury hadn't kept him out of Wimbledon.

So it might not be long until Sampras slips to third on a list he figured to top for a while.

Although it is often said that sports records are made to be broken, some are made of straw and others of stone, and many of much weaker or stronger stuff than the record-setting athlete imagines. Very few prove worthy of the distinction of unbreakable.

At the 1968 Summer Olympics in Mexico City, Bob Beamon set the world record with a long jump of 8.9 meters (29-feet-2½). He didn't know he broke the record until his coach Ralph Boston told him.

How long did he think he'd hold it?

"I thought somebody was going to break it during that competition," Beamon said recently.

Instead, it stood for 23 years, until Mike Powell jumped 8.95 meters at the World Championships. Beamon remains the Olympic record-holder.

"I have been very, very blessed as far as having this record stand around for this long," Beamon said.

That's how Mark Spitz felt when Michael Phelps figuratively swam past him in 2008.

Spitz not only set individual Olympic and world records at the 1972 Summer Olympics in Munich, but his overall achievement served as a record of its own: seven gold medals during one Olympics.

"You know, I never really sat around thinking about it," Spitz recalled earlier this year, before giving a speech in South Florida. "Records are made to be broken, and someday somebody would come around with the talent to challenge it. And I knew at the 2004 Games in Athens, Phelps challenged it, he got six gold medals and two bronze medals. So I knew he had the capacity and capability if everything went right to get seven gold medals or maybe even eight."

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