The Australian has had a very difficult 2017 as his mother has battled serious illness, while a big dip in form has also seen him suffer out on the golf course.
As such, Day has taken the decision to drop father-figure Day from the bag in order to preserve their friendship.
"Unfortunately it just didn't work out," Day revealed ahead of the BMW Championship in Chicago. "I'm trying to find my footing here. I had to do it at some point."
Day plans to use a friend Luke Reardon on the bag this week and says he wants to keep Swatton as his coach.
"He's just coming off the bag and going to more of a coaching role," Day said. "He's not out of my world one bit. I'm hoping things move forward with us like they always have ... because we both love each other like family."