The NFL Players Association has told its members that the union "tentatively agreed" that 40 players will take blood tests for HGH each week during the season, with a positive result drawing a four-game suspension.

The NFLPA emailed players a memo in question-and-answer format Tuesday. The Associated Press obtained a copy.

According to the email, players participating in NFL training camps this year will provide a blood sample for a "population study" to determine what level of HGH will result in penalties.

While Tuesday's memo says owners and players "will likely finalize soon" the in-season weekly HGH testing, the union does not indicate what the NFL has agreed to — or give specifics about what stands in the way.

A league spokesman declined to comment on the union's memo.

Copyright 2013 The Associated Press.