Major League Baseball has issued a warning to its players about the use of deer-antler spray, a substance administered under the tongue that includes a banned chemical known for its muscle-building and fat-cutting effects. Sports Illustrated first reported the story. Players felt free to use the spray at nearly no risk until the warning was sent last week by the league. In its warning, the league requested players not use the spray because it contained "potentially contaminated nutritional supplements" and had been added to the league's cautionary list of products. The warning was not issued because the spray includes the banned chemical, according to the report.