Williams (shoulder) began playing catch Saturday, Anthony DiComo of MLB.com reports.
It's the first time Williams has done any sort of throwing since he landed on the injured list Aug. 10 with a strained right shoulder. He still has several more hurdles to clear before he can return from the injured list, but the Mets expect the 31-year-old closer to return to the bullpen sometime in September. Until then, Kodai Senga figures to continue receiving the bulk of save opportunities.