Who has the edge in the Chase, Jimmie Johnson or Brad Keselowski?

It’s that time of year.

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

That’s not to say that the sort of misfortune that quashed Denny Hamlin’s title aspirations in Sunday’s TUMS Fast Relief 500 at Martinsville can’t happen to Jimmie Johnson and Brad Keselowski.

A part can break at any time, as did a bolt to the master switch on Hamlin’s 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.’s car collided with Johnson’s 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 series’ most venerable short track, rallying from a 32nd-place starting position to post a career-best finish — sixth.

“It’s like being in a war and surviving a battle,” Keselowski said after the race. “It’s not necessarily a win — you’re just happy to still be living.”

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? Here’s 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 NASCAR’s playoff format in 2004, and he’s never finished lower than sixth in the final standings. This is Keselowski’s first taste of life as a contender in NASCAR’s 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 last three venues would seem to favor Johnson, but a close analysis indicates that may not be the case. Keselowski believes Texas and Homestead, both 1.5-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 there’s 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.

Johnson’s real edge comes at Phoenix, scheduled between the two intermediates. In terms of career-average finish — with the exception of Kentucky and its small sample size (two races) — Phoenix is Johnson’s best track. The five-time champ has four wins in 18 starts there and an average finish of 5.3 to Keselowski’s 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 Johnson’s five championships, but in his second full season with Keselowski, Paul Wolfe is a master strategist and a budding superstar on the pit box. Knaus orchestrated the repairs of a wrecked car at Kansas, and Johnson drove it to a top-10 finish, keeping the No. 48 in title contention. Wolfe’s calls were integral to putting Keselowski in Victory Lane in the first Chase race at Chicagoland. No edge here.

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 — intelligence, judgment, calculated aggression, car control — neither has a decisive advantage.

Fuel Mileage: A clear edge here for Keselowski, whose Dodges have consistently outperformed the other manufacturers in fuel economy. Johnson is well aware that all three of the final Chase races could turn on gas mileage — that’s why the No. 48 team has been working diligently to improve in that area. If two of the final three races turn into fuel-mileage contests, however, superiority in that area could propel Keselowski to the championship.

Qualifying: It’s not where you start but where you finish. That’s the axiom, but Keselowski has been playing with fire on Fridays. Yes, his cars have been capable of driving to the front in race trim, but in qualifying 22nd, 20th, 25th and 32nd for his last four starts, Keselowski has put himself in positions that are vulnerable to the vagaries of the back markers. Poor results in time trials haven’t hurt him yet, but there’s no reason to tempt fate. The real death knell to Hamlin’s 2010 title effort was a 37th-place qualifying effort at Homestead, which led to an early spin in traffic on Sunday.

Keselowski’s two wins in the Chase have come from starting positions of 13th at Chicagoland and 10th at Dover. He must improve in time trials for the last three races to have a realistic shot at Johnson, who has two poles in seven Chase races. In fact, Keselowski has been giving up, on average, 10.7 positions to Johnson at the start of every race. If he continues to do that, Johnson will be hoisting his sixth championship trophy.