The opening line started at -1.5 in Indianapolis' favor and hasn't moved much since then. Some Vegas books have the Colts as high as 3 points, but this matchup is one of the bigger tossups in Week 2.
The Colts gave Survivor League players a scare in Week 1, needing a late rally to beat the Oakland Raiders, 21-17, and they obviously failed to cover the 11-point spread. The Dolphins beat the Cleveland Browns, 23-10, in their opener and comfortably covered as +2.5 point underdogs.
The current over-under is 42.5, which may be hard to come by since neither team reached that number in their respective matchups last week. There are no major injuries to report for either team. Indianapolis' defense could have a hard time covering the spread if it don't improve on its performance against Oakland.