(NEXSTAR) – Arizona Cardinal’s star receiver DeAndre Hopkins tweeted, then deleted a message saying his future as a player in the NFL might be in Jeopardy after the league issued a memo saying teams that experience a COVID-19 outbreak could have to forfeit games.

“Never thought I would say this, But being put in a position to hurt my team because I don’t want to partake in the vaccine is making me question my future in the NFL,” the tweet read, according to a screenshot from The Athletic.

Hopkins isn’t the only player pushing back against receiving the vaccine despite a number of players testing positive for the virus last year, causing several games to be postponed.

Bills receiver Cole Beasley has drawn widespread scrutiny on social media this offseason for his steadfast commitment to remain unvaccinated, which is often accompanied by misinformation.

NFL Commissioner Roger Goodell warned the 32 teams Thursday in a memo obtained by The Associated Press that no games would be rescheduled under such circumstances. Instead, forfeits could happen.

“As we learned last year, we can play a full season if we maintain a firm commitment to adhering to our health and safety protocols and to making needed adjustments in response to changing conditions,” Goodell said.

He added that the league does not anticipate adding a 19th week to accommodate games that need to be moved because of coronavirus issues.

“If a game can’t be rescheduled and is canceled due to a COVID outbreak among non-vaccinated players on one of the competing teams, the team with the outbreak will forfeit and will be deemed to have played 16 games for purposes of draft, waiver priority, etc,” Goodell added.

For purposes of playoff seeding, the forfeiting team would be assessed a loss and the other team a win.

If there is a virus outbreak because of a “spike in vaccinated individuals, we will attempt to minimize the competitive and economic burden on both participating teams,” the memo said.

The NFL has not made vaccinations mandatory. The league and the NFL Players Association, however, are strongly urging team employees and players to do so.

Last year, in the height of the pandemic, the NFL completed its season, the playoffs and Super Bowl on time. But it had contingency plans for an 18th week to play makeup games if needed. There were several postponements but no cancellations.

For 2021, the regular season has been expanded to 17 games.

The league says more than half its teams currently have COVID-19 vaccination rates greater than 80% of their players, and more than 75% of players are in the process of being vaccinated. All training camps will be open by the end of next week.

Nearly all clubs have vaccinated 100% of their Tier 1 and 2 staffs — essentially players, coaches and other club members who have direct contact with the players. Teams have appropriate protocols set up for staffers who have not been vaccinated, consistent with the guidance given last April.

The players’ union, in response to Goodell’s memo, reminded its players that “the same basic rules applied last year.”

“The only difference this year is the NFL’s decision to impose additional penalties on clubs which are responsible for the outbreak and the availability of proven vaccines,” the NFLPA memo said Thursday.

“The protocols we jointly agreed to helped get us through a full season last year without missing game checks and are effective, when followed.”

Other key points in the league’s memo:

— If a vaccinated person tests positive and is not symptomatic, he or she will be isolated and contact tracing will promptly occur. The positive individual will be permitted to return to duty after two negative tests at least 24 hours apart, and will thereafter be tested every two weeks or as directed by the medical staffs. Vaccinated individuals will not be subject to quarantine as a result of close contact with an infected person.

— If an unvaccinated person tests positive, the protocols from 2020 will remain in effect. The person will be isolated for a period of 10 days and will then be permitted to return to duty if not symptomatic. Unvaccinated individuals will continue to be subject to a five-day quarantine period if they have close contact with an infected individual.

— Those who had a previous COVID-19 infection will be considered fully vaccinated 14 days after they have had at least one dose of an approved vaccine.

The Associated Press contributed to this report.