KAZAN, Russia (AP) -- Competing in his first major event since his doping suspension was revealed, China's Sun Yang led the 400-meter freestyle heats Sunday as the traditional pool events at the swimming world championships opened.
Sun touched in 3 minutes, 44.99 seconds, winning his heat just an arm length ahead of Britain's James Guy, who qualified second in 3:45.37.
Ryan Cochrane of Canada was third in 3:45.86, while Australians Mack Horton and David McKeon failed to make the eight-man final, which was scheduled for later at the Kazan Arena.
China's anti-doping agency revealed in November that Sun served a three-month ban earlier that year after testing positive for the banned stimulant trimetazidine.
Sun won the 400 free at the last two worlds plus the 2012 London Olympics.