Indiana Pacers forward Glenn Robinson III will undergo surgery on his injured left ankle and is expected to be out of the lineup until mid-December, league sources told ESPN.

Robinson had missed most of training camp and the preseason with a high ankle sprain, and the necessity now for a surgical procedure will extend his original two-month timetable on a return for an additional two to four weeks, league sources said.

Robinson suffered the injury Sept. 29 in a scrimmage during practice, crumbling to the floor after a drive to the basket.

The Pacers consider Robinson, 23, a key part of the franchise's rebuild and plan a prominent role for him in the post-Paul George era.