This is his way of keeping her memory alive.
And also ...
"It's my way of saying sorry," Williams said. "That's why I wear the necklace, that's why I wear the pink glove. That's why I always have her with me, every single day."
Williams, 30, grew up in Honolulu with two older brothers and a very strict upbringing.
He was, as he'd tell you, "momma's little boy."
But then Williams became a first-round Draft pick as a teenager in 1999, and then, somewhere along the way, he got selfish.
"I didn't care about anything," Williams said. "I wanted to do what I wanted to do. I was 18 years old, I had all this money in the world, I had all my friends, I had everything. And all I wanted to do was go out and have fun. Never stayed home, never went to sit by my mom's side. Never."
Williams' mother was first diagnosed with breast cancer during his sophomore year of high school and recovered two years later.
Then in November 2000, the disease came back.
Williams can recount that day in vivid detail. It was in Las Vegas. His mom was driving, his father was with him in the car and the three of them were making the trek to San Diego to meet with Williams' agent. Then Deborah lost vision in her left eye, the car swerved and the three pulled over.
A week later, tests in Hawaii revealed the cancer had returned. And shortly after that, death became a foregone conclusion.
"My mom and our whole family are fighters," Williams said. "That first time it happened, she fought through it. Second time it happened, you can see her fight through it until that certain point, you see her like, 'I give up.' So we knew it was going to happen, we just didn't know when."
But Williams doesn't believe he was there for her enough during that time. At least not initially, when he was more focused on soaking up his newly attained popularity than being with his bedridden mother.
"It never woke me up until the day my dad told me, 'Stay home and be with your mom,' and when I did do that, I sat next to her, and from that moment, what she said, it triggered in me that I needed to stop," Williams recalled.
"I remember talking to her, and the words that came out of her mouth, it broke me down. 'What the hell are you doing here? Get the hell out my face.' ... So I left."
Angry, ashamed and remorseful, Williams stayed with his girlfriend, with whom he had just had a son, for a couple of days before finally swallowing his pride and returning home.
"From that point on," Williams said, "I think I grew up."
And mostly, he stayed put. He didn't leave his mother's side for two full months, until it was time to report to Spring Training in mid-February. Weeks after that, Deborah passed, prompting Williams to fly back home for the funeral.
But before then, in that bedroom in the Honolulu house they shared, mother and son got close again, rekindling a bond that got lost in adolescence.
In some ways, Williams is thankful for the time they shared in her final days.
But in some ways, he's still trying to make up for lost time.
"I regret whatever I did to her," Williams said. "Whatever I did, I regret. I wish I never did that in my life."
Williams and his electric fastball found success early in his Major League career, posting a 3.92 ERA while averaging 21 starts per season from 2003-05.
Then he got cocky, gained a lot of weight and watched as his career spiraled.
Prior to a fateful move to the Angels, who took a chance by signing him off the Lancaster Barnstormers of the Atlantic League last June, Williams jumped through six Major League organizations, was released twice, pitched two stints of independent ball, spent a year in Taiwan and, for a while, lost hope.
"I don't think I would've ever gone through that road if my mom was still here," Williams said with a smile, "because she would've been on my [butt] every single day."
But Williams' mother was with him.
He wore the puka-shell necklace she gave him on her death bed every day until it broke, then put the shells in a Ziploc bag and began sprinkling them throughout his uniform. Then early in 2011, he began sporting a pink Zett glove he got custom-made in the Far East.
"The first time I saw it, I was like, 'You have to be kidding me,'" Williams said. "It's a pink glove. Nobody uses a pink glove. And I got some heat for it when I was in independent ball and Triple-A [with the Angels]. But then I'd tell them about it and they'd be like, 'Oh, OK.'"
Williams' life is back to normal now. He has four kids, is happily married and is finding success as the final member of a loaded Angels rotation.
His mother, he believes, is here to enjoy that with him.
"She's always here," Williams said. "No matter what I go through, she's going to keep helping me. Every time I go to the field, I always remember what she taught me. She taught me everything."