Reid Spencer
NASCAR Wire Service

Itís that time of year.

Barring disaster for the top two drivers, the Chase for the NASCAR Sprint Cup is a two-man race.

Thatís not to say that the sort of misfortune that quashed Denny Hamlinís title aspirations in the Tums Fast Relief 500 on Sunday at Martinsville canít happen to Jimmie Johnson and Brad Keselowski.

A part can break at any time, as did a bolt to the master switch on Hamlinís No. 11 Toyota on Sunday. A stuck throttle can send a car hurtling into the outside wall, as was the case with Jeff Gordon in the first Chase race at Chicagoland.

A sudden twitch by another driver can trigger a wreck that wipes out one of the leaders, as was the case when Sam Hornish Jr.ís car collided with Johnsonís in the 2009 Chase race at Texas.

In 2009, however, Johnson had a large enough margin to absorb a 38th-place finish. This year, his margin heading to Texas is razor-thin.

In winning at Martinsville, Johnson turned a seven-point deficit entering the race into a two-point advantage. Keselowski also accomplished his objective at the Cup seriesí most venerable short track, rallying from a 32nd-place starting position to post a career-best finish ó sixth.

ďItís like being in a war and surviving a battle,Ē Keselowski said after the race. ďItís not necessarily a win ó youíre just happy to still be living.Ē

Clint Bowyer left Martinsville third in points, 26 behind Johnson. Kasey Kahne is fourth, 29 back. Neither has a realistic shot at the championship if either Johnson or Keselowski simply stays the course.

Between the two frontrunners, who has the edge? Hereís a breakdown of the relevant factors.

Experience: A clear edge here for Johnson, who has been through the Chase meat grinder in five championship-winning seasons. Johnson is the only driver to have qualified for every Chase since the inception of NASCARís playoff format in 2004, and heís never finished lower than sixth in the final standings. This is Keselowskiís first taste of life as a contender in NASCARís premier series. If he gets one hand on the trophy, will nerves set in, as they did with Hamlin in 2010?

Race Tracks: On the surface, the past three venues would seem to favor Johnson, but a close analysis indicates that might not be the case. Keselowski believes Texas and Homestead, both 1Ĺ-mile intermediate speedways, play to his strengths. Johnson has one career win at Texas, none at Homestead. Johnson has but 12 top fives in 29 starts at the two tracks combined, suggesting that thereís room for Keselowski to make inroads. True, Keselowski has never posted a top 10 at either Texas or Homestead, but he has made a habit of outperforming expectations this year. His first career top 10 at Dover, for instance, was a win in this Chase.

Johnsonís real edge comes at Phoenix, scheduled between the two intermediates. In terms of career-average finish ó with the exception of Kentucky and its small sample size (two races) ó Phoenix is Johnsonís best track. The five-time champ has four wins in 18 starts there and an average finish of 5.3 to Keselowskiís 22.2. Keselowski did finish fifth there in March, however, and will need a similar result to keep pace with Johnson.

Crew Chiefs: This category is a dead heat. True, Chad Knaus is the architect of Johnsonís five championships, but in his second full season with Keselowski, Paul Wolfe is a master strategist and a budding superstar on the pit box.

Drivers: Another dead heat. Both Johnson and Keselowski are elite talents and equally fearless. Both are at the top of the chart in terms of the feedback they provide to their teams. There are some differences in style and substance: typically, Johnson does the driving and leaves the strategy to Knaus, while Keselowski is more of a decision-maker behind the wheel. But in terms of the metrics that matter ó intelligence, judgment, calculated aggression, car control ó neither has a decisive advantage.