Jason Day's partnership with caddie Steve Williams is over after six tournaments.
Day told the Australian Associated Press that Williams will no longer be on his bag, citing a "disconnect" between the two after missing the cut at the Northern Trust.
"Parting with Steve was a mutual decision and not an easy one to make," Day told AAP. "He is the ultimate pro; it was a real learning experience being exposed to a caddie who has achieved what Steve has. He has worked with the best.
"But it was a disconnect of old school and new school. Steve has become a friend, and I have a lot of respect for him. I thank Steve for everything he taught me."
Day initially hired Williams-who rose to public prominence with Tiger Woods, and also worked for Greg Norman, Ray Floyd and Adam Scott-because, according to Day, he had "severely underachieved." The duo enjoyed initial success at the U.S. Open (T-21) and Travelers Championship (T-8).
"I've got a lot of work to do," Day said in Hartford. "Like we say, we're focusing on trying to win this year, but definitely trying to project and look forward to 2020."
However, Day reverted to his early season struggles, missing two of his next four cuts, his best finish a T-40 at the no-cut WGC-FedEx St. Jude Invitational.
The former PGA champ is 50th in the FedEx Cup standings, needing a massive push at the BMW Championship to make it to the season finale at East Lake. With a week to go before the automatic Presidents Cup picks are announced, Day is also on the outside looking in on the International squad.
According to the AAP, Day will have friend and fellow pro David Lutterus as his loop in Chicago.