The NFL Players Association advised players Tuesday not to attend voluntary in-person workouts with their teams this offseason, citing ongoing concerns related to the coronavirus pandemic.

The advisory by the NFLPA came as it continues to negotiate with the league over teams’ offseason workout programs for players. The union is seeking for teams’ offseason programs to be entirely virtual for a second straight year. The league wants teams to be able to return to in-person workouts and offseason practices. Teams are scheduled to begin offseason programs Monday.

“We find ourselves still in the midst of a pandemic with no comprehensive plan to keep players as safe as possible, yet teams are pressuring players to attend voluntary workouts,” the NFLPA said in a statement posted to the Twitter account of its executive director, DeMaurice Smith. “The union has advised players that given the continued risk of exposure and the goal of a full 2021 NFL season, that they should not attend these voluntary workouts. It is every player’s decision but our advice is to continue to use an abundance of caution given the current environment.”

The union reiterated its stance in a memo sent to all players Tuesday by Smith and JC Tretter, the Cleveland Browns center who is the NFLPA’s president. Players on three teams — the Denver Broncos, Seattle Seahawks and Tampa Bay Buccaneers — announced through the NFLPA Tuesday that they will not attend voluntary offseason workouts. New England Patriots players said Wednesday through the union that “many” of them will not attend the workouts.

The bulk of each team’s offseason program for players is voluntary, although teams also are permitted to conduct mandatory minicamps. Some players have bonuses written into their contracts that incentivize attending offseason workouts. Tretter and the NFLPA have contended that on-field, in-person offseason practices create unnecessary health and safety risks for players, arguing that the quality of play last season was not diminished following the entirely virtual 2020 offseason.

But some coaches and teams counter that the offseason practices are beneficial, particularly for younger players. Teams followed strict protocols last season, and the league seems to believe it is safer for players to work out in NFL facilities than elsewhere. According to a person familiar with the league’s view, the Broncos have had 22 players participate in informal workouts in their facility this offseason. A dozen teams have had 15 or more players in their facilities for informal workouts.

The NFL told teams in a memo Wednesday that the offseason programs will last nine weeks beginning Monday. For the first four weeks through May 14, all team meetings are virtual and there’s no on-field work for players. The first on-field work is scheduled for May 17; team meetings remain virtual that week. The final phase of the offseason programs begins May 24 and lasts until June 18. Then, teams can have in-person meetings and can conduct 10 days of on-field practices known as organized team activities (OTAs) and a mandatory minicamp.

In the meantime, negotiations between the league and the NFLPA over the offseason programs are expected to continue.

The NFL instructed teams to make every effort to have vaccines available for players, staff members and their families during the initial phase of the offseason programs. According to a person familiar with the situation, the NFL is proposing that vaccinated players would be subject to reduced coronavirus testing, would be exempt from contact tracing and would have increased opportunities to meet in person, eat in teams’ cafeterias and gather away from teams’ facilities. All of that is subject to a potential agreement with NFLPA.

The league took another step Tuesday toward, in its view, making teams’ facilities safer. The NFL told teams in a memo that coaches and other staffers must be vaccinated for the coronavirus, barring a valid exemption, to be permitted to work with players.

“Tier 1 and 2 employees (other than players) should be expected to be vaccinated unless they have a bona fide medical or religious ground for not doing so,” the league said in its memo. “Any staffer that refuses to be vaccinated without either a religious or medical reason will not be eligible for Tier 1 or 2 status and therefore will not be permitted access to the ‘football only’ restricted area and may not work directly or in close proximity with players.”

The league previously said it would not mandate vaccinations for players but would encourage and incentivize players to be vaccinated. A person familiar with the NFLPA’s view said at the time that was consistent with the sides’ discussions on the topic to that point.