The Cleveland Guardians have become the latest professional sports team to implement a COVID vaccine mandate, warning employees that anyone who doesn’t comply by Jan. 3 will face "termination," according to one report.

An email sent to employees last month, obtained by FanSided, informed them that they must be fully vaccinated by Jan. 3 unless given an exemption and must receive the first dose by Dec. 20.

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"To be fully vaccinated, two-weeks must have passed after receiving either the second shot in a two-shot vaccine (Pfizer or Moderna) or the only shot of the single-dose Johnson & Johnson Vaccine," the email reportedly in question read.

A worker from the Brilliant Electric Sign Company holds a broken piece of the Cleveland Guardians team store sign in Cleveland, Friday, Nov. 19, 2021, in Cleveland. The sign was being installed and fell off the building. (AP Photo/Ken Blaze)

"That means that – absent any exemption – all Executive Office and Service Level employees must receive either their second Moderna/Pfizer shot, or single Johnson and Johnson shot by December 20, 2021. Remember: there is an approximately three-week (Pfizer) or four-week (Moderna) gap between the first and second doses of the two-dose vaccines, so meeting these deadlines will require advanced planning. Failure to comply with this Policy will result in termination."

The Guardians did not immediately respond to Fox News’ request for comment.

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Workers begin to remove the Cleveland Indians sign from above the scoreboard at Progressive Field, Tuesday, Nov. 2, 2021, in Cleveland. Known as the Indians since 1915, Cleveland's Major League Baseball team will be called Guardians. (AP Photo/Ron Schwane) ((AP Photo/Ron Schwane))

The deadline for Cleveland’s team employees comes one day before the Biden administration’s mandate.

On Tuesday, the administration asked a federal court to let it move ahead with a workplace rule that would require employees at larger companies to be vaccinated against COVID-19 or face weekly testing.

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U.S. President Joe Biden and First lady Jill Biden disembark from Air Force One at Nantucket Island, Massachusetts, U.S, November 23, 2021. REUTERS/Tasos Katopodis (REUTERS/Tasos Katopodis)

If it stands, the OSHA rule would take effect Jan. 4 and apply to private companies of 100 employees or more, affecting roughly 84 million workers across the U.S. They would have to be vaccinated or be subject to weekly tests and required to wear masks at work. There are exceptions for employees who work from home, alone or outdoors.

The Associated Press contributed to this report.