SONOMA, Calif. -- The Verizon IndyCar Series season is down to six drivers competing in two events for one trophy. Actually, it's simpler than that.

It's Team Penske's title to lose.

Will Power takes a 39-point lead over teammate Helio Castroneves into Sunday's penultimate race, the GoPro Grand Prix of Sonoma at Sonoma Raceway. If either driver ends the weekend with a 95-point lead over the others still in contention, the championship will belong to Roger Penske's organization. The lead over those challengers is currently 92 points.

Winning a series title always means something, but it's even more significant this year because Team Penske has been dominated in recent years by Ganassi Racing. Chip Ganassi's team has won IndyCar's championship five times in the past six years, including the 2008 and 2013 titles by Scott Dixon, who remains eligible for this crown.

Team Penske last won the title in 2006 when Sam Hornish Jr. was driving. Coincidently, Hornish will attend Sunday's race as a television broadcaster for NBCSN. Maybe that's good luck, too, although Penske's team hasn't needed it much at this track.

Since 2010, Power has won three poles and three races, and he finished second in the race he didn't win. Even that race was stamped by a Penske car as Ryan Briscoe won in his final season with the team.

Team Penske not only enters this event with Power on a roll from last week's short-oval victory at Milwaukee, it has Juan Pablo Montoya as one of the hottest drivers in the sport. CART's 1999 champion finished second last week and is fifth in the standings, although 114 points out of the lead and a longshot for the title.

IndyCar returned to this 12-turn, 2.385-mile track in 2005, which means Montoya hasn't raced an open-wheel car on it. But, he has NASCAR experience here.

Simon Pagenaud of Schmidt Peterson Hamilton Motorsports and Andretti Autosport's Ryan Hunter-Reay are the two most likely to break the Team Penske momentum, but they have a lot of work to do. Pagenaud trails Power by 92 points, Hunter-Reay has a 108-point deficit.

The season ends next week at Auto Club Speedway in Fontana, Calif., and it's a double-points event. Gaining 95 points there is mathematically possible, but a driver needs to be within about 70 points to have a reasonable chance of capturing the title.

Or, it will be a Team Penske party.

The other thing to watch over the next two races is a new face in victory lane. Ten drivers have reached the top step of the podium this season, and that's one short of the sport's single-season record set in CART in 2000 and '01.

This year's winners include Power, Castroneves, Pagenaud, Hunter-Reay, Montoya, Dixon, Sebasten Bourdais, rookie Carlos Huertas, Mike Conway and Ed Carpenter. Marco Andretti is one to watch; he captured the 2006 race at Sonoma. James Hinchcliffe is another eyeing victory after scoring three wins last season.