It's easy to write off the Grizzlies since they have turned the page from the long-time, respected Mike Conley/Marc Gasol era. Memphis has a new coach, untested Taylor Jenkins, and is in rebuild mode.
Miami, though, is nothing special. The Heat were just three games better than the Grizzlies last season, failing to make the playoffs at 39-43. That was the third time in the last five years the Heat didn't qualify for the postseason. 
The Heat have undergone change, too. Dwayne Wade retired. Underrated Josh Richardson is gone. So is Hassan Whiteside, their top rebounder and shot blocker. But Miami is getting some love because of Jimmy Butler. 
Yes, Butler definitely will be the best player on the court. Justice Winslow has upside. Bam Adebayo may be underrated. But Miami isn't that good of a team. The Heat also is dealing with a distraction brought about by idiot Dion Waiters ripping coach Erik Spoelstra. Waiters is suspended for this game cutting into Miami's bench and concentration level with his insubordination. 
I really like Memphis' young talent and athleticism. I believe the Grizzlies are below-the-radar at this opening juncture and present good value getting this many points against a borderline Eastern Conference playoff team that went 19-22 at home last season.
The Grizzlies have an intriguing young nucleus of Ja Morant and Jaren Jackson Jr. Rookie Brandon Clarke could be good, too. Jackson and Jonas Valanciunas, who is expected to play, give the Grizzlies a big man edge.
All in all, it's enough to back the Grizzlies in this matchup.