NFL Commissioner Roger Goodell has written an open letter to fans explaining the NFL's strict policy against bounty systems such as the one league investigators have said they uncovered in New Orleans.

Goodell says this year there will be "clear, consistent and renewed emphasis" on enforcing the NFL's longstanding bounty prohibition.

Goodell describes bounty programs as those which provide incentives for plays resulting in injuries, or even "for performance against an opposing player, group of players, or team."

The commissioner says such programs undermine both the integrity of the game and the league's efforts to "aggressively protect the health, safety and long-term livelihood" of players.

The NFL has heavily sanctioned the Saints since concluding the club had a bounty program, including a season-long suspension of coach Sean Payton.