JaJuan Johnson also had 17 points for the Celtics, adding six rebounds. But the Celtics were blitzed from the beginning, falling behind by eight points at the end of the first quarter and 17 by halftime.
Behind a second-half resurgence from Jared Sullinger (11 points, seven rebounds), the Celtics briefly cut the lead to single digits. But Detroit regained control, riding the steady hand of point guard Brandon Knight (19 points, 14 assists) to victory.
Austin Daye added 15 points and eight rebounds for the Pistons. Jamar Smith (13 points) and Dionte Christmas (10) also reached double figures for Boston.
The Celtics are now 3-1 in the summer league. They play the Orlando Magic on Friday morning at 10 a.m.
For more news on the Boston Celtics, make sure to check out CelticsBlog.