The Colts offensive scheme, at its very core, is vertical in nature so it has commonalities with the Coryell system, including terminology and route trees. Beyond that, it's been customized and tweaked to such a degree that it isn't really that close to any other offensive system in the league.

Tom Moore is the godfather of the system, and he worked under Chuck Noll in Pittsburgh as the receivers coach. He coached up Lynn Swann and John Stallworth. His predilection is to get the receivers vertical to stretch the defense and hit the inside receivers between the numbers.

So for those arguing about the Colts offensive system, it is closer to the Ravens', but not THAT close. The Ravens run the most traditional Air Coryell in the league, and possibly the most traditional Coryell since the 1980's, but I think Caldwell will be fine from a QB coach perspective within the system.