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."

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

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