The 26-year-old missed the entire season last year with the Philadelphia 76ers, and expects a backlash on his return to the franchise on Friday night.
"Retirement was a thought, it was a serious thought. It still is," he said, according to ESPN.
"It's tough to enjoy the game because of how limited I am physically. I'm working through that. Every now and again I do [think about retirement]. It's still career-threatening. I'm a shell of myself on the court right now. I'm just struggling mentally."
Bynum has played in four games so far this year, averaging 5.5 points and 3.5 rebounds in 13 minutes per game.