Some NFL owners have proposed changes that would significantly strengthen the penalties for players who hold out in training camp in recent collective bargaining talks, according to sources.

The owners involved would like to increase the penalties for players who hold out. Currently, a team can fine a player up to $40,000 for each day of training camp missed and an amount equivalent to one week of the player's salary for each preseason game missed.

It would appear unlikely that the NFLPA would agree to changes that would hurt players' abilities to exercise their leverage in contract disputes without some significant financial concessions from the owners.