Interesting thought. I'm reminded of how with minimal offseason practice time and zero preseason games Brian Hartline was able to instantly have perfect timing with Tannehill. Hartline read the defenses correctly and ran precise routes and seemed to seamlessly mesh with Tannehill even as a rookie. Their timing seems flawless even today (except for the deep ball). So, I wonder if it has anything to do with the receivers maybe being at fault? Let's look:
Hartline: Instant timing, returned this year and continues to have excellent timing
Wallace: New to the team this year, new to Tannehill, new to this type of offense ... not yet developed timing
Gibson: New to the team, new to Tannehill ... took a few games but had developed timing and then got injured
Matthews: Second year player who is spotty with good timing on most plays and what appears to be poor reads on others
Keller: New to the team, new to Tannehill, new to this type of offense ... looked like he had established good timing with Tannehill in pre-season until he left with a season-ending injury
Clay: Returning player who has always been considered raw regarding reading defenses and running routes but with excellent athletic ability ... improving but not there
Sims: Rookie, new to the NFL, new to the team, new to Tannehill ... still has a ways to go with route running and reading defenses
Egnew: Returning player with a lot of physical ability ... seems to be progressing slowly
So, is it Tannehill that is the problem? Maybe, but most of what I'm seeing suggests that newness and receiver issues are the most prominent factor for the slow timing development. If it were Tannehill then I wouldn't have expected to see such quick development with Hartline, Keller and Gibson. The Keller and Gibson reps slowed the development of some of the others as well.