FRISCO, Texas -- If the NFL Players Association has its way, 18 Dallas Cowboys could have to forfeit a little more than $5 million in base salary in 2021.

Last week, Cleveland Browns center JC Tretter, the NFLPA president, urged players to skip the voluntary offseason programs that begin next week across the league.

If that were to happen, quarterback Dak Prescott, defensive end DeMarcus Lawrence, receiver Amari Cooper, running back Ezekiel Elliott, linebacker Jaylon Smith, guard Zack Martin and tackles Tyron Smith and La'el Collins could have to forfeit $500,000 each from their base salary because of a de-escalator for missing at least 84.375% of the Cowboys' offseason program.

Prescott, who signed a four-year, $160 million deal that included a record $66 million signing bonus, has a $9 million base salary.

Tight end Blake Jarwin, linebacker Tarell Basham and cornerbacks Anthony Brown and Jourdan Lewis have $250,000 de-escalators. Kicker Greg Zuerlein, cornerback C.J. Goodwin, tackle Ty Nsekhe and defensive ends Brent Urban and Carlos Watkins have $100,000 de-escalators. Safety Darian Thompson has a $50,000 de-escalator.

Defensive end Randy Gregory doesn't have a de-escalator like the other 18 players, but would forfeit the $180,000 offseason workout bonus that is part of the one-year extension he signed last year.

The only part of the NFL offseason that is mandatory is the June minicamp. Traditionally, the Cowboys have had near 100% attendance at the voluntary program, in part because almost all of the players live in the area all year.

Tretter wrote on the NFLPA website, "many of the changes this past year -- like no in-person offseason workouts/practices, the extended acclimation period before training camp and no preseason games -- gave us a year of data that demonstrates maintaining some of these changes long-term is in the best interest of the game."

The NFL moved to a virtual offseason program last year because of the coronavirus pandemic.

Phase I of the offseason program begins Monday, and players will be allowed to work out at the team facilities in small groups under the COVID-19 protocols. In a memo to the teams last month, the NFL said meetings early in the offseason program will continue to be virtual, but it does not anticipate an entirely virtual offseason program in 2021.

A plan for in-person, on-field work -- such as organized team activities and the minicamp -- has not been agreed to as of yet.