Ryan Briscoe held off Penske teammate Will Power to take the win at Sonoma, although the latter's championship hopes received a huge boost when many of his rivals struck trouble.
“It's big. I wasn't sure if I was ever going to win again," admitted Briscoe. "Especially here in Sonoma, I've always done so well at this track and I got my first-ever pole position here (2005) so it's great to finally get the win. Great battle with Will at the end there."
Briscoe gained the lead on a pit stop sequence on lap 65 when he hit the blend line ahead of Power, who had pitted a lap earlier but was caught behind traffic during a full-course caution.
"He definitely had some bad luck in the pits, but we were there all day," Briscoe added. "This is definitely a confidence-builder."
Power blamed slow backmarkers rather than the pit stop, however.
"I had the quickest car, quite easily keeping a handy lead," related Power. "We had a slow stop, probably lost four seconds there, then came across a bunch of guys on the track who just doddled all the way back. I don't know who those guys were. That's when I was using the word 'wanker'. Cost me the race.
"But, I couldn't be happier for Ryan. He really needed that win. He's been strong all weekend. But, yeah, I can't help but be a little bit disappointed. We led heaps and then we didn't."
Briscoe was forced to defend his advantage through two late restarts, but he held his teammate off on both occasions and crossed the line 0.4sec clear. Dario Franchitti was third, the Scot having spent the last few laps trying unsuccessfully to find a way past Power.
"We've definitely been giving something up to them all weekend," Franchitti said of the Penske cars. "We definitely have some work to do, the Target team and Honda, to close the gap. It was good to follow those guys so closely, because I think I have a good idea of where that advantage is..."
Power's disappointment at missing the win was countered by the misfortunes that struck the main threats to his title. Ryan Hunter-Reay was in a strong position for most of the afternoon before being hit by Alex Tagliani. The American spun, stalled, got a push-start, and then found himself being penalized a few laps later for running into EJ Viso. Two of the other title contenders were derailed in the same incident when Helio Castroneves turned Scott Dixon around at the start.
Castroneves was penalized for his part in the incident, while Dixon worked his way back into the top 10 only to damage his front wing in a trip through the dust while fighting Hunter-Reay.
Rubens Barrichello had his best IndyCar result, delivering a fourth place for KV Racing. The Bourdais/Newgarden incident meanwhile had ramifications for both drivers, with Dragon writing off Bourdais' chassis and Newgarden sustaining an injury to his left index finger.
Results - 85 laps:
Pos Driver Team/Car Time/Gap
1. Ryan Briscoe Penske Dallara-Chevy 1m17.2709s
2. Will Power Penske Dallara-Chevy + 0.4408s
3. Dario Franchitti Ganassi Dallara-Honda + 1.0497s
4. Rubens Barrichello KV Dallara-Chevy + 8.8529s
5. Graham Rahal Ganassi Dallara-Honda + 9.4667s
6. Helio Castroneves Penske Dallara-Chevy + 11.2575s
7. Simon Pagenaud Schmidt Dallara-Honda + 12.3087s
8. JR Hildebrand Panther Dallara-Chevy + 22.8121s
9. Alex Tagliani Herta Dallara-Honda + 39.6868s
10. Tony Kanaan KV Dallara-Chevy + 1 lap
11. Justin Wilson Coyne Dallara-Honda + 1 lap
12. James Jakes Coyne Dallara-Honda + 1 lap
13. Scott Dixon Ganassi Dallara-Honda + 1 lap
14. Mike Conway Foyt Dallara-Honda + 1 lap
15. Sebastian Saavedra AFS/Andretti Dallara-Chevy + 1 lap
16. EJ Viso KV Dallara-Chevy + 1 lap
17. Simona de Silvestro HVM Dallara-Lotus + 1 lap
18. Ryan Hunter-Reay Andretti Dallara-Chevy + 1 lap
19. Oriol Servia Panther/DRR Dallara-Chevy + 1 lap
20. Ed Carpenter Carpenter Dallara-Chevy + 1 lap
21. Charlie Kimball Ganassi Dallara-Honda + 3 laps
Sebastien Bourdais Dragon Dallara-Chevy 63 laps
Josef Newgarden Fisher Dallara-Honda 62 laps
Katherine Legge Dragon Dallara-Chevy 48 laps
Marco Andretti Andretti Dallara-Chevy 46 laps
James Hinchcliffe Andretti Dallara-Chevy 35 laps
Takuma Sato Rahal Dallara-Honda 2 laps