"There is a possibility we will make Danny available because of Nathaniel Clyne coming through," Warnock told the South London Press.
"I've really got to look at areas I want to improve and it may mean letting one or two players leave without damaging the squad. Danny is too good to not be playing regularly."
Butterfield, 29, was loaned to Charlton last season after losing his place to Clyne in the Palace side.