Thaddeus Young scored 18 points, though he didn't play in the fourth quarter of what became a blowout. Tony Wroten added 18.
The Sixers (17-61) shot 44 percent for the game.
The Grizzlies, who at tipoff were a game behind Phoenix for the eighth seed in the Western Conference, played like a team fighting to hang on to its playoff hopes. A 65 percent shooting effort in the first quarter to go along with an 11-point output from big man Marc Gasol put the 76ers in a 30-24 hole.
Gasol finished with 21 points and 10 rebounds. Miller chipped in with 19 points on 8-for-11 shooting off the bench.
The 76ers clawed back to get the lead under double-digits just before the break. Young hit a long two with 1:15 left to pull the Sixers within eight, but a Zach Randolph layup in transition a minute later carried the Grizzlies into the half with a 57-47 lead.
Though the game threatened to get away from them at the end of the first half, the 76ers didn't lie down without one last-ditch effort. Young, one of the only bright spots for the 76ers in the game, hit a straightaway three to cut the lead to 63-57 but was forced to sit after picking up his fourth foul midway through the third quarter.
The Grizzlies' long rotation ultimately wore down the 76ers, who have struggled to find consistent and reliable depth this season. By the end of the game, 13 Grizzlies players had logged minutes.
Tony Allen added 15 points for Memphis.
Memphis, led by its post players Gasol and Randolph, took advantage of the Sixers' thin interior with a 49-36 rebounding edge.
When Young re-entered the game with 4:44 left in the third period, the Grizzlies' lead had ballooned back up to 14. Gasol hit a straight-away three-pointer, only his second of the season, with 3.5 seconds left in the third to give the Grizzlies an 87-64 advantage heading into the fourth.
It was not a banner day for Rookie of the Year candidate Michael Carter-Williams. He scored eight points on 4-for-13 shooting and also picked up a technical foul in the third quarter for jawing with an official.
For Elliot Williams and newly acquired Adonis Thomas, last night was a sour homecoming; both played college basketball at the University of Memphis, which plays its games at FedEx Forum. Williams and Thomas scored 13 and four, respectively.
The 76ers conclude their three-game road trip tonight at Charlotte.