Natalie Coughlin was upset in the women's 100-meter freestyle final Tuesday at the Pan American Games, finishing second to Canada's Chantal van Landeghem.
Coughlin had a strong start and led for about the first half-lap but battled with Van Landeghem and Arianna Vanderpool-Wallace down the stretch. Van Landeghem, pleasing the hometown crowd in Toronto, finished with a personal-best 53.83 and was followed by Coughlin (54.06) and Vanderpool-Wallace (54.15).
"I'm riding the pain train big time tonight," Coughlin said after the last of her three Tuesday races. "This morning was a really controlled 53.8, so I was like, 'I'm gonna go so much faster tonight.' I haven't had a chance to look at my video yet, but I think I stuck to my race plan more or less. It was just a matter of execution. So I need to go back and see where I went wrong. But honestly, 54.0 is pretty good, and the 53.8 that I went in the morning is my fastest time in five years, so I'm gonna take it.
"I knew a 53 mid to low was in me. It was about executing it, and I just didn't do that tonight."
Coughlin, a 12-time Olympic medalist who was the heavy favorite going into the evening final, lost later in another showdown with Van Landeghem in the 4x100 freestyle relay. The U.S. team lost the lead during Coughlin's anchor leg against Van Landeghem and finished second to Canada.
Coughlin, who will turn 33 in August, is trying to make her fourth U.S. Olympic team for next summer's Rio Games. She switched coaches and set about tweaking her training and technique. She has also logged personal-best times in two events since the 2012 London Olympics, including an American record in the 50-meter backstroke in June at the Santa Clara, California, stop of the Arena Pro Series.
A bout of severe food poisoning, of all things, helped derail her bid to qualify for next month's world championships in Russia. She had to settle for the Pan American Games; it is her first time at the event.
ESPN.com senior writer Bonnie D. Ford contributed to this report.