Power currently holds a 50-point lead over Castroneves, while Pagenaud trails by 81 points. Castroneves earned a bonus point for winning Friday' qualifying at Fontana. Power qualified 21st, and Pagenaud placed 13th.
This 500-mile race is the third an final leg in IndyCar's "Triple Crown" this season, and it awards double points. A driver could earn a total of 104 points, if he were to qualify on pole, lead the most laps and win the race.
If Power finishes sixth or better in this event, he will claim his first IndyCar championship, regardless of where Castroneves or Pagenaud finishes. Castroneves, a three-time Indianapolis 500 winner, and Pagenaud are seeking their first titles in the series as well.
Power won last year's season-finale at Fontana. It was just the second time in his IndyCar career that he had won on an oval. His third and most recent victory on an oval took place earlier this month at The Milwaukee Mile.
"It was definitely a great finish to last year," Power said of his 2013 win at Fontana. "Now, it's a different field, and actually things just get tougher and tougher all the time in this series. Winning last year definitely doesn't make me feel comfortable going in. I know that it's going to take a lot of hard work and a very good race to win the championship, so I'm just focusing on the things I can control."
Power finished second in the IndyCar championship in three consecutive seasons (2010-12). He placed fourth in points last year.
In 2010 and '12, Power entered the season-finale as the points leader. Four years ago, he came to Homestead-Miami Speedway with an 11-point advantage over Dario Franchitti, but Power ended up finishing 25th there after he made contact with the wall and sustained heavy damage to his right-rear suspension late in the race. Franchitti's eighth-place finish allowed him to clinch the title by just five points.
When the series held its season-ending race in Southern California for the first time two years ago, Power entered it with a 17-point lead over Ryan Hunter-Reay. Power crashed early in the event and wound up finishing 24th. Hunter-Reay claimed the championship by only a three-point margin following his fourth-place run.
Power is hoping he won't encounter any mishaps in this race.
"To me, it's just aim for a top-five finish, absolutely," he said. "The mindset is just to really work hard on getting the car right. Obviously, the rest you can't control. So just really focusing on the job that I have to do."
Castroneves finished second to champion Scott Dixon in IndyCar points last year. Dixon came to Fontana with a 25-point lead over Castroneves.
A fifth-place finish for Dixon coupled with Castroneves' sixth-place run allowed Dixon to clinch the title by 27 points.
So what will it take for Castroneves to beat Power for the championship?
"Good question. What is it going to take?," Castroneves wondered. "It's going to take to win a race and hopefully things go in that direction. We're working hard together, and come up with a little bit of luck too. It's not only in my control.
"But the good news is we have this thing pretty close to Team Penske, and I believe our goals will be accomplished, and that's what we're looking for. But yes, I'm going to do everything I can to bring that side, and we've just got to keep ourselves in the hunt and doing all we did last year, push as much as we can so that if it happens, it happens."
Pagenaud will obviously need a lot of luck to win the title.
"It's pretty simple, I just have to go into weekend very focused on trying to be competitive and go into the race thinking to win the race," Pagenaud said. "That's the only way I could have a chance to win the championship. I don't have any pressure. We've done really well this season with this Schmidt Peterson Motorsport team and now we're in a really good position. It's nice to come to the last race with a chance to fight for the championship."
Twenty-two teams are on the entry list for the MAVTV 500.
Series: Verizon IndyCar. Date: Saturday, Aug. 30. Race: MAVTV 500. Site: Auto Club Speedway. Track: 2-mile oval. Start Time: 10:20 p.m. ET (expected green flag). Laps: 250. Miles: 500. 2013 Winner: Will Power. Television: NBC Sports Network. Radio: IMS Radio Network/SIRIUS XM Satellite.