I find this line too short. Miami is at least one level higher than Portland, has a strong home-court advantage and situational elements favor the Heat, too.
Miami is 16-1 at home. That's the best home mark in the NBA. Portland is 7-12 on the road and has failed to cover in five of its last six away matchups. The Trail Blazers also are 0-5 ATS the last five times taking points. 
The Heat should be fired-up after suffering an embarrassing 20-point loss to Orlando two days. 
This marks Portland's third road game in five days. The Trail Blazers took advantage of a decimated Washington squad to beat the Wizards, 122-103, this past Friday. Before that victory, the Trail Blazers had lost five straight.
The Trail Blazers are thin up front with big men Zach Collins and Skal Labissiere out. 
This is the first meeting of the season between these teams. Miami swept Portland last season winning the two games by an average of 9.5 points. The Heat are much improved this season while Portland has severely regressed.