Butler (knee) is still in the relatively early stages of his recovery and has only recently begun getting back on the court, according to Danny Emerman of SFStandard.com.
There remains significant uncertainty surrounding his return timeline, as his injury typically carries a nine-to-12-month recovery window. A return sometime between Christmas and March appears to be a reasonable range for now, though fantasy managers shouldn't put much stock into a specific target date until Butler progresses further in his rehab.