UPDATE (2:40 PM ET): ABC's Doris Burke has reported on-air that Rondo has suffered an ACL tear and will be lost for the season. The Celtics have confirmed this report.
Sources within the organization broke the story to the Boston Herald's Mark Murphy, saying that knee injury Rajon Rondo suffered in the Celtics' last game against the Atlanta Hawks could have been an ACL tear.
The injury was initially thought to be a hyperextension and not much more. Rondo played 45 minutes against the Hawks but was a late scratch in today's game against the Miami Heat.