The OP makes a critical point. In the passing game, the importance of a left tackle, especially for a right handed quarterback, rises or falls with the voluntary or instinctive mobility of the signal caller.
Much emphasis has been put on Dak Prescott in his young career to stand tall in the pocket. Sometimes that emphasis has contributed to him holding the ball too long. That makes him an easier target for pass rushers. He is an easier target if his blindside blocker is a ready made turnstile.
Unless the offense plugs the hole made by Smith's absence, it should be Kellen Moore's primary responsibility to adjust the passing offense where Prescott is either rolling away from pressure or throwing to receivers running quick routes. It may bring back dislike for dinking-and-dunking but there are no other alternatives if you cannot give Prescott time to throw intermediate and deep passes consistently.
Smith sidelined impacts the running game as well. Even with tight end blocking help, run plays will probably execute best going right than left. Defensive coordinators will gameplan to half the offensive line's blocking scheme with Smith not on the field.
The hole must be plugged by a replacement who will excel. A Smith version 2.0 is not necessary. What is needed is a guy who will consistently give Prescott 2 or 2 1/2 seconds on passing snaps and stonewall penetration on run plays for four quarters. A guy who can get to the second level and run interference for a second on toss plays would be gravy too.
