Two-time major winner Thomas splits with caddie Mackay
Thomas, who won the 2017 and 2022 PGA Championships, began working with Mackay in September 2021 after a break for the caddie following 25 years with Phil Mickelson.
"While incredibly difficult for me to say, Bones and I have parted ways," Thomas posted on X, formerly Twitter. "I'm going to be forever thankful for him joining me on the bag in 2021.
"The things we've been able to accomplish together -- the PGA Championship in 2022, the Presidents Cup, the Ryder Cups were all unforgettable experiences. His wisdom on and off the course has been a blessing during a tough stretch of my career and he was there every step of the way.
"I know there are great things coming for both of us down the road. I wish him the best of luck and will always count him and his family amongst my friends."
It is unclear who will carry the bag for Thomas when he tries to win a green jacket on April 11-14 at Augusta National.
Mackay, 58, was the bagman for Mickelson for five of his six career major triumphs, including all three of his Masters victories.
He also caddied for Thomas when he won the 2022 PGA Championship at Southern Hills, the most recent professional win by the 30-year-old American.
Thomas missed last year's PGA Tour playoffs but had a solid start to the 2024 campaign with four top-12 finishes in seven events.