The Celtics agreed to a two-year, $2.7 million contract with Williams on Thursday, NBA reporter Marc Stein reports.
The rookie second-rounder latched on with Boston on a one-year, two-way pact this past summer, though he's now been upgraded to a standard deal. The 24-year-old big man has appeared in 13 regular-season games (two starts) so far this season, during which he has averaged 1.7 points and 2.1 rebounds in 8.2 minutes per contest. He'll continue to provide center depth for Boston behind Nikola Vucevic (recently traded), Neemias Queta and Luka Garza.