The former Wales winger has been training with the Chiefs during the summer after quitting rugby in January to pursue a career in the NFL.
The 23-year-old did not participate in the NFL’s “cutdown day,” but he did play in all three of their preseason games.
Teams must choose 53 players from their 90-player offseason training group before the season begins; the deadline for doing so was Tuesday.
However, Rees-Zammit’s chances of participating in the regular season are not gone.
He is anticipated to continue working out with the Chiefs as a member of their practice squad even though he will now be placed on waivers, allowing another team to sign him.
The NFL champions can promote him to their active roster up to three times during the season, giving him extra time to adjust to the sport. Every game, two players from the practice squad can be promoted by NFL teams.
A 10-week training camp as part of the NFL’s International Player Pathway (IPP) marked the start of Rees-Zammit’s NFL career.
The Chiefs, who have won the last two Super Bowls, signed him after that. Despite being targeted as a running back, he filled in at several spots throughout the preseason as the Chiefs attempted to do so.