Zach Randolph had 17 points and 12 rebounds for Memphis. Reserve guard Marcus Williams finished with 16.
"It was the defensive intensity in all four quarters, especially in the first quarter," said Mike Conley, who led the Grizzlies with seven assists. "You've got to have that firepower out of the gate. That led to a lot of easy buckets for us."
Will Bynum led the Pistons with 19 points on 6-of-8 shooting, and Ben Gordon scored 13. Charlie Villanueva had 12 points in his first game with Detroit.
Gay made seven of eight shots from the field and had 20 points in the first half to lead Memphis to a 68-46 lead at the break. He missed his only two attempts in the second half, but also finished with seven rebounds and four assists.
"They did a wonderful job of transition, taking care of the basketball and sharing the basketball," Pistons coach John Kuester said. "What we have to do as a team is to become better in our transition defense. We also need to be better at on-the-ball defense. We really struggled."
Both coaches lobbied the replacement officials pretty heavily in the first quarter, but sometimes it took an introduction to make their point. At one point, Memphis coach Lionel Hollins had to ask press row for the name of official Eric Hanspard, before calling out to get his attention.