He is about to begin pre-season training with the back-to-back Super Bowl champions after signing a three-year contract. But Rees-Zammit is only guaranteed to be paid for the first year and his deal, worth up to £2.27 million, could be terminated at any time by Kansas City.
"As a rookie you sign a three-year deal and you get guaranteed money. So if you get injured or you get cut, you're still guaranteed that money," Rees-Zammit told the Rugby Pod.
"But you can get cut at any point so it's bit of a cut-throat sport. I could go to pre-season now, not do well and just get cut straight away.
"You're not guaranteed the three years at all - and no one is. I just need to make the 53-man (senior) squad now. I'm ready to show everyone what I can do."
Rees-Zammit said in January he was leaving rugby union to explore an NFL career and became part of the NFL International Player Pathway Program, created in 2017 to help global athletes make their way into American football.
He may be aided in his quest to forge an NFL career by rule changes regarding kickoffs, which were converted to a more rugby-style catching and run back format with kicks from well behind a spread-out line - only Rees-Zammit would have the aid of blockers on kick returns.
"The new kick off rules this year are absolutely massive," Rees-Zammit said. "That's where my main position will be and I've got to fight to start in that position this year."
He added he had already been in touch with two of the Chiefs' biggest star players in quarterback Patrick Mahomes and tight end Travis Kelce.
"Pat and Travis both messaged me," said Rees-Zammit. "Pat's my best mate now! They said welcome to KC and if I ever need anything then let me know. I'm so excited to meet everyone and get training."
