HOMESTEAD, Fla. — Brad Keselowski got some help on the last day of practice for NASCAR's Sprint Cup season finale at Homestead-Miami Speedway.

Pole sitter Joey Logano was involved in a three-car accident during the first of two practice sessions Saturday, switched to a backup car and will start from the rear of the field Sunday.

That will move Keselowski, who had qualified third, to the front when the green flag drops Sunday. Marcos Ambrose will start on the outside.

And if Keselowski leads the first lap, he will extend his points lead from 20 to 21 in the 400-mile race. He needs to finish 15th or better to clinch the title, which would be the first for longtime NASCAR team owner Roger Penske.

"I certainly wasn't expecting to be on the front row," Keselowski said. "It's different from what we're used to, but it's different in a good way. ... If I can take the lead without wrecking myself, then that's what I'm going to do."

Keselowski seemed a little tighter than usual Saturday, quite possibly starting to feel the pressure as he goes for his first championship.

Fellow title contender Jimmie Johnson, who will start 10th in the finale, has done all he can to make Keselowski feel uncomfortable.

"Ready to race for sure," Johnson said. "Very pleased with how our car finished up. It's really nothing for me to lose sleep about tonight. It's an easy night for me. ... Easy from my standpoint because I've got nothing to lose. We'll see what they do on the other side."

Johnson also thoughts about how he would like see the first lap unfold.

"I hope (Keselowski) tries really, really, really hard to lead that first lap," Johnson said. "I know Ambrose next to him is going to try hard, too. That could be good for me."

Keselowski knows Johnson is messing with him and is a little envious of his position.

"I don't ignore it, but if we could change places, I bet he would in a heartbeat," Keselowski said.

Keselowski was faster than Johnson in practice Saturday. Keselowski turned the faster lap and edged Johnson with a better 10-lap average.

"I think we're a top-five car right now," Johnson said. "Winning? We'll work on that tonight and put some final touches on it. But I knew coming into this weekend I was going to have a big hill to climb with the (No. 2) car and the points lead that they have. They've done their part; they've been very competitive all weekend long.

"We'll just have to see how that race goes tomorrow."

At least one competitor believes Keselowski's No. 2 Dodge has a decided advantage over Johnson's No. 48 Chevrolet.

"Those guys are executing really well, and from what I've seen so far this weekend, I just don't think the 48 has the speed to run with those guys anyway," Joe Gibbs Racing driver Denny Hamlin said. "So I think that they're going to have to rely on something catastrophic happening to the 2."

The championship contenders avoided both wrecks in practice.

Hamlin and Greg Biffle were running side by side, with Logano right behind them on the outside, when they made connect and started spinning. Logano got caught up in the mess.

"I was the innocent bystander once again and drove into it," Logano said. "It's unfortunate."