Mission's Brent Hayden says he's learned his lesson, and left nothing in the pool Tuesday morning in qualifying for tonight's semifinals of the 100-metre freestyle at the London Olympics.

The 2007 world champion, swimming alongside the defending champion James Magnussen of Australia, qualified fifth among 60 swimmers in 48.53 seconds, just behind Magnussen's 48.38.

American Nathan Adrian qualified No. 1 at 48.19.

"It was good to have [Magnussen] there on the back end because that's where he's strongest. It's like worlds last year, I was beside Adrian and he kind of pulled me along on the front end," Hayden said.

"I don't know if where I am situated is really going to play into it, but I've just got to race, no matter what. I'm holding nothing back. I made that mistake in Beijing because I had a relay that night and I think it kind of played into my head -- and combine that with a little too much confidence being world champion the year before, I thought I had room to save energy so I didn't really focus on just making sure I got into the final.

"But I'm just not going to make that mistake this time."

The 28-year-old said "tonight could be the last time I race an individual 100-metre freestyle, so I gotta race like it's my last race."

His time was nowhere near his personal best 47.27, let alone Brazilian Cesar Cielo's three-year-old world record 46.91 - before the controversial bodysuits were banned - but Cielo was even slower Tuesday, qualifying 10th in 48.67, and said "I think I'm going to focus more on the 50." Yannick Agnel of France qualified 12th in 48.9

"For the heats, it's pretty deep," Hayden said of the times. "There weren't really a lot of amazing times - Adrian's 48.1 in the morning is very good, but the rest of the guys are just all solid.

"But tonight, those times aren't going to matter, whether you're first, second or third or you're the 16th guys making it into the semifinals, everybody's going to be jumping."

In the men's 200m butterfly, Scott Dickens of Ancaster, Ont., won his heat in 2 minutes, 10.95 seconds, a half-second under his personal best, to qualify 13th for the semifinals.

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