Like many of the other players who have decided to sit out, Williams did so to protect a close family member from potentially contracting COVID-19. The running back revealed Thursday that his mother was recently diagnosed with stage 4 cancer.
"My mom is my rock, my everything. During a hard time like this, I think I should be next to her (for) every step," Williams told SiriusXM NFL Radio.
"My mom, she just was like, 'Whatever decision (you make), I'm behind you.' At the end of the day, it's hard," he added. "Football is my life, especially coming off a championship and wanting to do a repeat - which, you know, I know they're gonna handle that - but at the end of the day, this was something personal that I had to handle."
Williams had the best regular season of his career so far in 2019. He racked up 498 yards and five touchdowns on the ground and added another 213 yards and two scores through the air.
But the 28-year-old saved his best performance for the final game of the season. He scored two fourth-quarter touchdowns (one rushing, one receiving) to propel the Chiefs to a dramatic late-game comeback, finishing the game with 133 total yards.
Though the loss of Williams is a blow to a Kansas City offense that'll also be without guard Laurent Duvernay-Tardif, who was the first player to opt out, the AFC West club's backfield is well-prepared to thrive without him.
The Chiefs used their first-round pick on former LSU running back Clyde Edwards-Helaire, and now the rookie is tipped for a standout first season alongside Patrick Mahomes and Co.