One more shot at an individual Olympic gold. One more chance to put another 100 meters between him and the disappointments of Olympics past.
"People are going out real quick," said Hansen, who finished fourth in the 100 breaststroke at the 2008 Olympics and came up short of gold in the 100 and 200 at the 2004 Games despite setting world records in both events earlier that year. "I've got to figure out how to get out faster."
Hansen finished Saturday's semifinal in 59.78 seconds, nearly a full second slower than top qualifier Cameron van der Burgh of South Africa, who finished in an Olympic record 58.83 seconds in the lane adjacent to Hansen.
"It's tough to stay on your race pattern when you've got a guy like Cameron next to you that's going out that fast," said Hansen, whose best time ever is 59.13 seconds, set in 2006. He finished this year's U.S. Olympic trials in 59.68 seconds.
Saturday's semifinals shifted what had become an established pattern in the 100 breaststroke. While van der Burgh, who was third at the last two world championships, was the class of the field, Japan's Kosuke Kitajima, the two-time defending Olympic champion and Hansen's longtime chief rival, qualified sixth.
Eleven swimmers finished the semifinals in under a minute. Hansen's U.S. teammate, Eric Shanteau, didn't make the final with a 59.96-second finish.
"This is probably the fastest this event has ever been," Shanteau said.
Hansen's qualifying spot puts him in an outside lane in Sunday's final. The better, he said, for surprising his competitors.
"No one will ever see me out there," he said.
Hansen, 30, retired from swimming after Beijing but returned to the sport in January 2011. Shanteau was not surprised to see him make the final.
"Brendan's a racer," Shanteau said. "He always was. He's consistent. He's one of the best breaststrokers this sport has ever seen."
Australia won gold in the women's 400-meter freestyle relay, setting an Olympic record of 3 minutes, 33.15 seconds. The United States got off to a blistering start, but finished third with a time of 3:34.24. The Netherlands won the silver in 3:33.79.
China's Sun Yang won the men's 400 freestyle in Olympic record time, and 16-year-old Ye Shiwen set a world record in the women's 400 individual medley.
Sun came close to breaking the world record of 3:40.07 (held by Germany's Paul Biedermann), finishing in 3:40.14. The reigning Olympic champ, South Korea's Park Tae-Hwan, was second in 3:42.06, and America's Peter Vanderkaay was third in 3:44.69.
Ye's time of 4:28.43 smashed the world record of 4:29.45 set by Australia's Stephanie Rice at the 2008 Olympics in Beijing. Race favorite Elizabeth Beisel of the United States was second in 4:31.27, and China's Li Xuanxu was third in 4:32.91.