Grant Williams is currently playing his fourth season with the Boston Celtics, with his contract set to expire after the season. The forward joined the Celtics in 2019 after he was selected 22nd in the NBA draft, and he signed a four-year contract worth $11.8 million. Currently, Grant Williams is in the final season of his contract with the Celtics and is set to become a restricted free agent after the postseason concludes. His club option for the 2021-22 season was worth $2.61 million, and he opted to accept another club option this year, which will earn him $4.3 million before his contract expires. Furthermore, the Celtics offered him a qualifying offer worth $6.23 million, but as he is already a starter for the team, the offer increased to $8.48 million for one season.

During his rookie season, Grant Williams played 15.1 minutes per game, while in his second season, his numbers remained the same. However, in his third season, his growth as a player was noticed, as he became a knockdown shooter. This season, he has proved himself to be an important role player for the Celtics, currently averaging 8.1 points, 4.6 rebounds, and 1.7 assists, shooting an efficient 45.4% from the field. Celtics coach Joe Mazzulla praised Williams for bringing a level of physicality and poise to the team, and his knack for contributing and turning something good into something great.