NASCAR Phoenix 2013: Why is Jimmie Johnson competing in Saturday's Nationwide Series race?

Jimmie Johnson is competing in today's Nationwide Series Dollar General 200, his first start in the division since August 2011. But what's up with this strange one-off decision?

Johnson wanted more track time on the still newly configured Phoenix track surface, citing its importance as the second and penultimate races of the season respectively. But NASCAR testing regulations make it difficult for a team to test for a track like Phoenix so Johnson decided competing in the Nationwide Series was the best way to accomplish his goal.

Dale Earnhardt Jr., whose JR Motorsports team provided a car for Johnson's last Nationwide start, had an opening and a deal was quickly reached.

"I'm just truthfully trying to get better here at this track," Johnson said Friday at Phoenix. "It's tough to get laps on this track. We considered coming out and testing, but with the tire change and with them changing the testing policy for Cup, it just wasn't going to work. The next best thing was to run the Nationwide race. I have no clue what I'm going to learn from those cars that carry over. But reps on the track can't hurt and ultimately, that's what I think I need."

Johnson has been potent at the new track configuration but the Daytona 500 winner likely recognizes the importance of mastering the 1-mile Arizona speedway. Phoenix all but decided the Chase last year when Johnson cut a tire and sailed into the outside retaining wall and was forced to go to the garage. Brad Keselowski, his championship rival, took over the championship lead at the end of that race and did not relinquish it the following week at Homestead.

Phoenix will play the same crucial role on the schedule this year as in those past but with a new Cup Series car and Goodyear tire package, track time at one circuit could make all the difference in Johnson's pursuit of a sixth Sprint Cup Series championship.

Johnson has one victory in 92 Nationwide Series starts and finished second in his last attempt at Watkins Glen.