What makes a great NASCAR feud?

It is arguably the crown jewel of the NASCAR Hall of Fame. Beaten and battered, a Chevrolet and Oldsmobile sit next to each other, a screen between them displaying a crash and its aftermath.

If this sport was a built by the bricks of heated feuds, then without question its cornerstone is the brawl on the final lap of the 1979 Daytona 500 between Cale Yarborough and Bobby and Donnie Allison. It's the rivalry upon which everything that's come since must be measured against.

Nobody's going to confuse Greg Biffle and Boris Said's altercation on Monday at Watkins Glen with one of the seminal moments in NASCAR history. This was simply a sound-byte worthy spectacle highlighted by Said saying Biffle "needs a whupping and I'm going to give it to him."

But it got the Racing Fan thinking, do any of this season's feuds have the potential for greatness?

There are defining elements that make up the anatomy of a lasting rivalry. Yarborough vs. the Allison Bros. had those elements, but only one of this year's run-ins seems to fit the following criteria -- and it's not the one you'd expect.

More often than not, recent altercations have seemingly been over just as soon as they've started. At this point, Tony Stewart-Brian Vickers seems like ancient history, as does Juan Pablo Montoya-Ryan Newman, and considering Said's part-time status, we can expect the same from he and Biffle. A rivalry needs to build over time, not just offer fireworks for one or two weeks.

Kyle Busch-Kevin Harvick passes the test. It has been brewing since last year's finale at Miami, when Harvick intentionally wrecked Busch, and it lingered for months before coming to a head at Darlington.

Ditto, for Kurt Busch-Jimmie Johnson. The ill feelings between the two started long ago, but they really came to a head the last two years at Pocono. Last season J.J. claimed he was try to bump draft Busch at the Tricky Triangle, only Busch's Dodge wound up hitting the wall, setting off a chain reaction that left Busch's car destroyed. It only set the stage for their recent altercation at Pocono in which they exchanged paint during the race and words after it.

Any feud worth its salt must involve big personalities. It's why anything involving a Busch or Harvick is riveting.

Kyle and Harvick are notorious hot heads who have clashed with nearly everyone in the series. Put the two together and it's, to quote Eminem, "what happens when a tornado meets a volcano."

Kurt Busch had seemingly matured from the brash punk who was punched by Jimmy Spencer in 2003, but between his obscenity-laced radio rants and saying, "It's rubbing racing. I'm putting the 'R' back in racing," regarding his actions against Johnson, Kurt is recapturing his bad boy past.

Johnson is the antithesis of the former drivers, and anything involving him wouldn't seem to fit the bill. He's often been chastised for being too "corporate" or too boring, but he's the five-time defending champion and there's no bigger star, or personality, in the sport.

Kyle Busch is more than accomplished, with 100 career wins in NASCAR's top three circuits and a Nationwide title to his credit. So is Harvick, a two-time champion of the second series as well as a Daytona 500 winner. They're also legitimate contenders for the Sprint Cup championship this season.

But Johnson and Kurt Busch have already been crowned champions, and one of them (Johnson) may end his career with an argument in the Greatest of All Time debate, and that's the difference. It's the element that all the best rivalries in NASCAR history have had (Richard Petty-David Pearson, Petty-Bobby Allison, Yarborough-Darrell Waltrip, etc.).

Johnson-Busch is still brewing, and expecting it to take a place in the pantheon on NASCAR rivalries is probably a long shot. J.J. has always seemed too savvy to let anything get to him for long, and once the Chase begins, he's in a world all his own. But still, I'm reminded of a conversation I had with him last March.

It came after Bristol, a race in which Busch led 278 laps, only to finish third as Johnson reached Victory Lane. Busch threw a fit, then said, "To pour my heart and soul into this race to beat the [No.] 48 car, I was trying to hit my marks every lap. I feel exhausted, I feel disappointed."

I asked Johnson about that, about being in a driver's head and forcing that driver to wonder where his No. 48 is, even if that driver's dominating.

"To see [Busch] get out and throw stuff at his car and punch his car, it's comical," Johnson told me. "I'm glad that we're doing this to these guys."

But, for the first time in Johnson's reign, it's beginning to look like the roles have changed. Is Kurt Busch getting to him? The unflappable Johnson is showing signs, saying he's not going to let Busch "run his mouth."

"If I'm in his head," Busch said, "then he's got to worry about us running through the Chase."

Other rivalries may be more explosive, but we have yet to see anyone truly go toe-to-toe with Johnson -- until now. While this rivalry fits the criteria of a true NASCAR feud, it's that added element that makes it the one we'll be watching for the rest of the season.

Denny Hamlin. The pressure is on. After a 36th-place finish last week at Watkins Glen, Hamlin fell to 12th in the points, and while he's still in position to grab one of the wild-card spots for the Chase (along with Brad Keselowski), it's no given. Fellow one-race winner Paul Menard is only 27 points behind him with four races remaining in the regular season, and while Marcos Ambrose sits 50 points back, making a charge isn't out of the question in the new points structure.

Hamlin desperately needs a return to Victory Lane to all but secure a Chase berth, and it just so happens Michigan is one of his most prolific tracks. Over the past five races there, no one has more points than Hamlin's 726. During that stretch he has two wins (including one in June), a second, a first and a 10th. Expect Hamlin to continue that hot streak in Brooklyn, Mich.