Busch and 23XI Racing announced on Thursday
that Busch would not be able to return to Toyota for
next weekend's playoff debut in Darlington,
so he withdrew his medical exemption to participate.
While Busch will no longer be eligible for the Drivers' Championship,
the team will continue to compete for the Owner's Championship.
Bush, 43, made it to the playoffs in May with a win in Kansas.
The victory marked Bush's ninth consecutive year with a win.
Bush, 43, said, "As much as I wanted and was able to make the car
playoff runs with our team, it's still not the right time for me.