Stephens won her first Grand Slam title at the US Open, playing in just her fifth event since having foot surgery in 2016. But she didn't win another match for the rest of the season, losing six consecutive matches since Flushing Meadows.
"I pushed it a little bit too much just because I wanted to keep playing," Stephens said at the WTA Elite Trophy in Zhuhai, adding that she now planned to get "little bit smarter" about her schedule.
Kei Nishikori has also withdrawn from Brisbane with ongoing hip problems. Rafael Nadal, who withdrew from Abu Dhabi, is scheduled to play the competition.