NFL SPORTS

"We have a strong confidence that the testing program, as we have designed it, will sufficiently deter use, but also has a reasonable opportunity to detect the use of those who choose to do it," Birch said.

There are no valid statistics on what percentage of players use the banned substance, but media reports have speculated 10 to 20 percent of the league's players have tried it.

Birch said he did not believe it was that prevalent.