Kosuke Kitajima was beaten by American archrival Brendan Hansen on Monday. He had to settle for second place in the men's 100-meter breaststroke final at the FINA World Swimming Championships.
Kitajima could not catch the speedy Hansen down the stretch and touched the wall in 59.96 seconds.
Hansen, the world record-holder in both the 100 and 200, defended his title in 59.80 seconds.
"I'm disappointed. My time was slow. Both my time and Hansen's were slow compared to our best efforts," Kitajima said.
Kitajima, who won gold in both the 200 and 100 at the 2004 Athens Olympics, battled it out with Hansen in the early going but trailed the American in second at the turn and failed in his bid to win the title for the first time in two meets.
"I also tried my best in the second half of the race, but Hansen was undeniably stronger than I was."
In a tense showdown with his top rival, Hansen reached the midway point of the race in 27.67 seconds. Kitajima touched the wall in 27.79.
After the race, Hansen told reporters that "it was a battle."
The American added: "I'm not real pleased with the time, but you can't always break the world re ord. (Kitajima) is a great competitor. I couldn't see him, but I knew he was there. I just put the blinders on and experience came through."
In the semifinals, Kitajima had the fastest time (1:00.05), while Hansen was seeded second in the event with a time of 1:00.13.
Their rivalry has been one of the swimming's most interesting storylines this decade.
Hansen set a world record at the 2006 U.S. Nationals. Kitajima won the 100-meter gold at the 2003 World Championships in Barcelona, Spain, the same meet in which he set a world record in the 200.