No one's suggesting we use Montez the same way we used Sefo. For one, Sefo runs a 5.1 and he's only that fast in a straight line. You get Montez into open space on runs, because he can utilize it far better. Also if we're going to replace Sefo's reps in the run game with passes, then we better have some 4 WR sets and our OL better block better than they did for Sefo (and especially Montez) because he came up limping just as much from dropping back.
In fact, you seem to be ignoring in general that Sefo was injured on drop-backs more than he was on QB runs (he separated his shoulder on a pass, he hurt his wrist on a pass, he broke his foot on a pass, he twisted his ankle on an outside the box run, and I think he got injured in the last two games on drop-backs).
Lindsay can't really handle more reps and he lost his only respectable backup and a QB who took away a lot of the hits from him, I'm most worried about his health than anyone's.