Power moved into the lead on lap 196 when the two drivers in front of him pitted and he closed out the race to record his 34th career IndyCar victory. Patrick became the first woman to win an IndyCar Series race in 2008 when she won the Indy Japan 300.
"I'm not really sure what happened", a dejected Patrick said after coming out of the care center. "He's been in his yellow suit - I don't think I've seen him out of his yellow suit since we got here this month".
Patrick, 36, had those same thoughts as she returned to Indianapolis after her 2005 debut at the track that sparked her career.
Patrick left IndyCar and moved on to stock cars in 2012, but never won a race.
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Danica Patrick's career ended when she lost control and slammed into the wall. But he had just one top-three finish at this race before Sunday, and he screamed after exiting his auto, mouthing "I can't believe it" before dousing his head in milk. But she said this week that she didn't have any regrets about her career. "Now it's not just a hope, it's more of a reality that I've really got a shot at it".
Power, who started on the front row of the 500-mile (805 kilometres), 200-lap race, was on the charge after the final caution, coming home ahead of polesitter Ed Carpenter and 2008 victor Scott Dixon of New Zealand. "I've had so many wins, so many poles".
An IndyCar series champion and four times runner-up, Power delivered a cool, calculated drive on a sizzling hot day to reach Victory Lane, becoming the first Australian to win the famed race and giving owner Roger Penske his 17th Indy 500 success. He's one of the most decorated drivers of his generation.
"But I kind of said before I came here that I feel like if it's a complete disaster - "complete" like as in not in the ballpark at all, look silly - then people might remember that". And I don't know, maybe she's going to be fine. ("Please Roger, can I come back", he pleaded with team owner Penske in his television interview.) Fellow Brazilian Tony Kanaan, another former victor who had the lead early in the afternoon, later lost control in turn two and also exited the race.
Just before the singing of the national anthem, with the crowd as quiet as it would be all day, one fan screamed from the grandstands, "Let's go Danica!"