The NFL has sent a warning letter to Tom Coughlin following his criticism of players not attending voluntary offseason workouts.

Coughlin was not fined, but he could face a penalty if he makes future comments.

The NFL Players Association had asked the league to reinforce the rule about pressuring players to attend the voluntary workouts and to reach out to the Jaguars.

"We're very close to 100 percent attendance and, quite frankly, our players should be here building the concept of team, working hard side-by-side, constructing our bond of togetherness, formulating our collective priorities and goals," Coughlin said. "Success in the NFL demands struggle. Those who have everything given to them become lazy, selfish and insensitive to the real values of team. The hard work that many try to avoid is the major building block for the development of an outstanding football team.

"It's not about rights and privileges. It's about obligations and responsibility, and the question is, 'Can we count on you?'"