Boston led by 29 but had to hold on late for its fifth win in six preseason games as the Raptors rallied in the fourth quarter, outscoring the Celtics 39-16.
The Celtics led 101-73 heading into the fourth before the Raptors mounted a comeback against Boston's reserves. Toronto's
Rondo scored 16 of his points in the third, including a 12 for 15 showing at the free throw line, as Boston outscored Toronto 41-30.
Bargnani continued to struggle with his shooting, going 5 for 16. The top pick in the 2006 draft, Bargnani is 16 for 64 in five preseason games.
Boston forward Glenn Davis, who skipped Wednesday's win at New York with a sore left knee, returned to the lineup but fouled out after scoring five points in 10 minutes.
The Celtics shot 7 for 11 from 3-point range in the first half, including two each from Daniels and Robinson, to lead 60-43 at the intermission.