- By Justin Falconer

Jason Day and Steve Williams's partnership has been short-lived, after Day announced their decision to split.

The Kiwi will no longer be on the bag for Day after the pair came together at the US Open in July.

Day has missed the cut in two of his last three starts, including last week's FedEx Cup Playoffs opener in New York.

Fellow Australian pro David Lutterus will take up the role of Day's caddie starting this week at the PGA Tour's second playoff event, the BMW Championship.

"Parting with Steve was a mutual decision and not an easy one to make," Day told AAP following The Northern Trust.

"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 dropped ten positions on the FedEx Cup standings to 50th after missing the cut at The Northern Trust.

This week's 70-strong field will be trimmed to the top 30 on the standings after this week for the season-ending Tour Championship in Atlanta.