The 25-year-old has been swimming for much of his life. He earned a spot on the Junior National team at 12.
But back then, Hansen could not have imagined where he would end up.
In 2000, the year he graduated from Havertown High, he nearly made it to the Olympics. He had third-place finishes in the 100-meter and 200-meter breaststroke events in the Olympic trials.
In the 2004 trials, Hansen set world records in the 100 and 200 breaststroke. He was the first American to hold both records since 1974.
But he was unable to win a gold medal in either event at the Olympics. He won a silver in the 100 and a bronze in the 200.
Hansen also left Athens with a gold medal in the 400 medley relay. The Americans set a world record in the event.
But that group medal didn't satisfy Hansen. He wants a gold medal to call his own.
With that in mind, Hansen, who now lives in Austin, Texas, has dedicated his time to tedious training at the Longhorn Aquatics Club.
"I put a lot of hard work in, in the fall," Hansen said. "I feel stronger, and I'm about 2 or 3 pounds heavier than I was last summer. I think a lot of that's just straight muscle.
"So, as far as physically, I think I'm better than I was last summer. It's just what kind of mental state I'm going to be in."
The competition better beware if the breaststroke specialist is really in even better condition now.
Last summer Hansen was remarkable. He broke his 100 (59.13 seconds, from 59.30) and 200 (2:08.74, from 2:09.04) breaststroke world records, at the 2006 Summer Nationals.
And it didn't stop there. A few weeks later at the 2006 Pan Pacific championships, he did even better in the 200 (2:08.50).
"I think when you go into a summer like last year, and then going into the meet this year, there's only so much you can compare between the meets," said Hansen, a four-time NCAA champion at the University of Texas. "Last summer my motivations were definitely high after coming off the World Championships in 2005.
"I was the only member of my team not to break a world record, so it pushed me to really want to do that. I just went on a tear last summer."
Despite the dominance of the U.S. team, Hansen doesn't find it hard to get motivated. "We all feed off each other," he said. "That's why we've been successful in the past.
"As a team, we don't think about other teams. We really take a lot of pride in being dominant. We don't care who is second.
"There's not another powerhouse out there to compete with us, but that's not stopping us."
Hansen realizes that other swimmers are focusing on him more than others.
"I know what I did last summer and what I've done since the Olympics has just thrown a bigger and bigger target on my chest," he said.
"Overall, I think that it's the same competitors. It's going to be a battle."
But Hansen will never turn away from a challenge.
"I surround myself with people that don't let me get lax at all in workouts or in preparing for an event," he said. "[My coaches] see so much potential in me, but sometimes potential can be a killer on you.
"They continually try to push me, continually try to get me to reach new levels . . . That's a decision I made, to try to surround myself with those kinds of people.
"It's worked for me in the past, and hopefully it continues to work for me in the future." *