09:28 AM ET 03.09 | The NBA and National Basketball Players Association are close to an agreement to test players' blood for human growth hormone (HGH), according to sources with direct knowledge of the talks. Testing could begin as soon as the 2013-14 season. The NBA has long had HGH on its list of banned substances but has never tested for it. Doing so means collecting players' blood, which the union has never allowed, and there was little agreement about the test's reliability. But those concerns have eroded lately, sources say, with a frenzy of progress in talks between the league and union. A decisive factor: Major League Baseball and its respected union have agreed to blood tests for HGH, weakening the basketball union's claims that the test was unreliable or that blood testing is too invasive.