Former Chicago Bears linebacker Dick Butkus has slammed the NFL for its lack of testing for the human growth hormone.

Butkus believes that there could be players who would test positive for HGH and said that this puts "clean" players at a distinct disadvantage.

"It is inexcusable to not have HGH testing in place for the 2013 season," Butkus said in a statement. "If you care about the health and safety of players, you should not play without first conducting HGH testing.

"Guys playing clean in the NFL are getting the short end of the stick. They are being put at risk and penalised for doing things the right way.

"Most importantly, young players at every level are watching and paying attention. They are waiting for the players to lead."

Butkus is a Hall of Famer and made a total of 1,020 tackles in his career.