Rule of 72: Narrowing the field

Editor's note: An explanation of Ricky's "Rule of 72" can be found here.

After a wild weekend at Martinsville, I think we have four drivers still in the Sprint Cup battle: Kevin Harvick, Brad Keselowski, Tony Stewart and Carl Edwards. Matt Kenseth's 31st-place finish, according to the Rule of 72, eliminates him from the running. A 31st-place finish in the Chase is difficult enough to recover from, but Kenseth also posted an 18th-place finish the week before, so the two poor races combined make him the latest to fall:

As we get down to the final group of drivers still in contention, it makes more sense to take bonus points into consideration. Of the drivers remaining, Harvick is right at that 72 cutoff. If I were strictly enforcing the Rule of 72, he'd be done after the Texas race no matter what. But Harvick is carrying over 12 bonus points because of his wins prior to the Chase. That extra padding keeps him in the hunt.

Brad Keselowski, the next highest driver on the Rule of 72 leaderboard, is obviously still within striking distance. But there are two things that are hurting him right now: (1) His spin on the final few laps at Martinsville -- by my measure, that cost him eight to 10 points. (2) His lack of bonus points. At three wins, he has only one fewer victory than Harvick. But because he wasn't able to climb into the top 10 in the regular-season standings, he entered the Chase as a wild-card driver and wasn't eligible for bonus points. We didn't talk a lot about this at the start of the Chase, but as we get down to the last three races, those nine points are looking pretty significant.

Tony Stewart has been feast or famine in this Chase. His three wins were his only three top-five finishes. And of the other four races, he's had two finishes of 15th or worse. But I believe Tony Stewart's best two races will be the final two. I don't consider Texas -- where tire wear comes into play -- his best track. So if he can just keep things close, I can see him posting strong performances in Phoenix and Miami.

And then there's Carl Edwards. Some are critical of him not winning in the Chase. (In fact, he hasn't even finished second). But despite the unusual nature of his success, he needs to keep doing what he's been doing. If his next three races are third-place finishes and he goes on to win the title, he's not going to apologize to anybody. I really believe this is the strategy that his team has employed and he's done a great job, particularly recovering from some potentially damaging races.

The one thing that really concerns me is that Edwards is the only driver in the top 10 with zero DNFs this year. I'm a law of averages type of guy, and he's due for a rough race. A DNF could drop him from first to about fourth in the Chase standings.

But I don't think Edwards needs to win a race in this Chase to validate his championship run. The single biggest reason I feel that way? Edwards has won a race this year. I would feel differently if he hadn't found Victory Lane. But even still, the system is what it is and I think it favors winning more than it has in the past. But Edwards is finding a way to capitalize every week. At this point in the Chase, he and Stewart are the only two drivers to control their own destiny.

With three races to go and the "Jimmie Johnson factor" no longer in play, it will certainly be interesting to see how things play out.

Ricky Craven is a driver with wins in all of NASCAR's top three series, including rookie of the year titles in both the 1992 Nationwide Series and 1995 Sprint Cup series. He currently serves as a NASCAR analyst on ESPN studio programs.