TRACK AND FIELD
American 100-meter record holder Tyson Gay tested positive for a banned substance and said he will pull out of the world championships next month in Moscow. Gay wouldn’t reveal the substance in a phone conversation from Amsterdam on Sunday, but he said he was notified by the US Anti-Doping Agency late last week that a sample came back positive from a May 16 out-of-competition test. He said he will have his ‘‘B'’ sample tested soon, possibly as early as this week . . . Former 100-meter world-record holder Asafa Powell and Jamaican teammate Sherone Simpson have tested positive for banned stimulants, their agent told The Associated Press. Powell and Simpson tested positive for the stimulant oxilofrine at the Jamaican championships last month and were just recently notified.