McCaw saw Williams for the same condition in November.
The Raptors have said there is no timeline for McCaw’s return yet, and added that an update on his status will be provided if appropriate.
Toronto is unable to replace McCaw on the NBA campus with another player, so the team’s roster is 16.
McCaw has appeared in 37 games with the Raptors this season, averaging 4.6 points, 2.3 rebounds and 2.1 assists in 24.5 minutes. The 24-year-old hadn’t appeared in any of the Raptors games since the team moved to the NBA bubble, where the league plays the rest of its season in isolation due to the COVID-19 pandemic.
Toronto hadn’t lost a placement match in the bubble before a Friday game against Boston.