BALTIMORE -- With a victory in the Grand Prix of Baltimore, Will Power could have clinched his first IndyCar Series championship and made the final race of the year irrelevant.

Instead, the Australian finished sixth after starting on the pole in a race he won last year. Ryan Hunter-Reay's win Sunday moved him within 17 points of Power heading into the Sept. 15 finale on the oval in Fontana, Calif.

After blowing a late lead in the points race in each of the last two years, Power has every right to be nervous.

His sense of humour, however, remains intact.

"Good news is," the Australian staid, "if I take Hunter-Reay out in the last race, we crash out together, I win."

Sunday's race on a 2.04-mile street course drew nine caution flags, was marred by rain and had eight drivers drop out before the finish.

"I'm still trying to catch my breath," Hunter-Reay said. "Those restarts were crazy, crazy, crazy."

The last restart came five laps from the conclusion of the 75-lap race. While front-runner Ryan Briscoe was waiting for the green flag, Hunter-Reay caught sight of it and took off, moving from second to first.

Briscoe claimed Hunter-Reay jumped the gun, but race officials ruled otherwise.

"Everyone had been going late," Hunter-Reay explained. "The green flags were coming out before the leaders were accelerating, and I caught wind of that. So I just started to focus on the green flag instead of the guy next to me. Briscoe got jumped on that one, but the green flag was flying and he was sitting there in first gear."

Briscoe was second, rookie Simon Pagenaud finished third and Scott Dixon came in fourth.

Hunter-Reay leads the IndyCar series with four victories. He won three straight races on ovals at Milwaukee and Iowa and the street course in Toronto.

This one, however, was more meaningful than most.

"The championship was on the line today," he said.

Power fell out of the lead around the 20th lap to make a pit stop for a change to rain tires, a concession to the drizzle that pelted several sections of the track. The other top three cars opted to stay on slick tires, and Hunter-Reay moved in front.

The rain quickly subsided, so Power pitted on Lap 28 to change back to slicks. That pushed Power back to 17th, and although he eventually worked his way back into first, that advantage disappeared when he made his final pit stop.

"Every weekend, we are not just the quickest, but by a bunch," Power said. "And circumstances seem to prevent us from winning. Today, we lost it with the weather."

Briscoe insisted that the rules require that the drivers pair off while waiting for the green flag, and he said Hunter-Reay was intentionally lagging behind.

"I was honestly just waiting for him to pair up because he came off the chicane and he was hanging back," Briscoe said. "He accelerated from two car-lengths back before I accelerated, and that's not how restarts work."

That, however, is how they operated on this day.

"Definitely I jumped out and I'm happy about it," Hunter-Reay said.

And now, the pressure is on Power heading to the finale in California.

Michael Andretti, owner of the Andretti Autosport Team of which Hunter-Reay is a member, said. "I think we got them worried, and we should have them worried if he's not. We did exactly what we needed to do coming into this weekend."

Power is up for the challenge.

"If we thought three races ago we would have a 17-point lead, we would actually be pretty happy, so that's not bad," he said.

Dario Franchitti's season took another hit on Lap 21 when he spun to a stop after his car was clipped from behind by Simona de Silvestro. The collision damaged the front of Silvestro's car, and Franchitti eventually dropped out of the race.

He finished 13th.

"Very disappointing race for us," Franchitti said. "IndyCar officials need to take a look at what is and what isn't acceptable. This is becoming a full-contact sport."

Takuma Sato, who held the lead for a while, dropped out Lap 50 due to mechanical difficulties.

Sebastien Bourdais exited on Lap 32 with mechanical failure in the suspension. Bourdais was fourth in qualifying.