Just look at the preseason, and nevermind the "only playing against 3rd stringers" excuse, as Tannehill also played against 3rd stringer in preseason and didn't do anything. In 5 of the 8 drives that Devlin had in the preseason, he moved the ball the length of the field. Of all the drives Tannehill had in the preseason, we punted in almost all of them. Now in the regular season Tannehill has 1 TD in his last 30 drives. He cannot convert on 3rd down which a good quarterback has to do. He's not aware of winning the games, on third downs he throws short passes just to get completions that pick up 5 yards and bring up 4th down. 3rd down he takes off running and slides instead of trying to get the 1st down. You knew that once we were behind 7 or 10 points in the first quarter, we were done because he can't come back from behind or be depended upon in the clutch.
His tunovers and ineffectiveness cost us all the games we lost. I know there were other weak areas with the team in those games, but if he had played decent and didn't screw it up, we still win. Devlin rarely turns it over and consistently completes passes and moves the ball and wins games, just look at both of these quarterbacks college carreers.
I think even Philbin knows that Devlin gives us a better chance to win, but Philbin is not in control of that because of the investment and expectations this organization has in Tannehill.