Blown tire all but ends Jimmie Johnson's title hopes

• Johnson was running in top 10 when he hit turn 4 wall on lap 235
• He trails Brad Keselowski by 20 points with one race remaining
• Keselowski can clinch his first Cup title with 15th-place finish or better at Homestead-Miami

AVONDALE, Ariz. -- Jimmie Johnson and crew chief Chad Knaus are known for their calm, cool performances under pressure during the 10-race Chase that leads to the crowning of NASCAR's Sprint Cup champion.

Now, they will need one of the sport's greatest rallies for the five-time champion to win a sixth title after a blown right front tire sent Johnson into the turn 4 wall in Sunday's race at Phoenix International Raceway.

Johnson, who came into the AdvoCare 500 up seven points on Brad Keselowski, heads into this weekend's season finale at Homestead-Miami Speedway 20 points behind Keselowski, who finished sixth Sunday.

"It's way, way out of our control,'' Johnson said. "We can go down there and win the race and do everything on our behalf and it still won't net us a championship.

"It's unfortunate to have the day end like this and potentially our season, our hopes for a championship.''

Only four times since 1975 has the champion come from behind in the season finale to win the crown: Tony Stewart last year, Johnson in 2010, Alan Kulwicki in 1992 and Richard Petty in 1979. The latter three of those comebacks were under different points systems, and none of the four deficits were as great as what Johnson now faces.

Johnson had worked his way into the top 10 after qualifying 24th before the wreck on lap 235 of a scheduled 312.

Keselowski needs only to finish 15th to clinch his first Cup title. He also can clinch by finishing 16th with a bonus point for leading a lap or 17th and earning a bonus point for leading the most laps.

Johnson said he felt a slight vibration before the tire went. Goodyear spokesman Mike Siberini said that the tire failed because of a melted bead from brake heat.

"I knew my car was tight that run the tire exploded, but I didn't think we were going to have an issue with the tire going down,'' Johnson said.

Said Knaus: "That stuff happens. It's part of motor sports. It's kind of why we do it, to see what the outcome is going to be. If you knew what the outcome was going to be, it wouldn't be any fun to do it.''

Johnson said his woes make next week easier in one sense.

"It takes a lot of pressure off,'' Johnson said. "The position we're in now really is a go-for-broke mentality ... If they have some bad luck, it changes our game plan.''