49ers preseason grades vs. Titans: Jordan Mason shines, run defense flops

Defensive Position Tackle Grades

Run Defense: Kalia Davis vs. Ty McGill

The 49ers' run defense was porous, with a few phenomenal plays. The hope is that players who did not play, like free-agent acquisition Jordan Elliot, provide more backbone against the run. Against the Titans, rookie safety Malik Mustapha provided the most explosive highlight tackle, but Kalia Davis, a defensive tackle in his third year since being drafted, had a couple of explosive plays when he just blew up run plays by splitting the double-team. Davis also missed a couple of tackles, but his disruptiveness was important to see.

Ty McGill Jr. was disruptive as well, but not in a positive way. With two neutral-zone infractions, McGill's day was completely overshadowed by a couple of mental blunders.

In a fight to round out the 49ers' defensive line depth, Davis got the upper hand.

Davis's Grade: B/McGill's Grade: D+

Pass Defense: The Cornerback Depth

The presumptive top-three cornerbacks on the 49ers did not play against the Titans, leaving the rest of the deep cornerback room to battle it out for what may be only two or three roster spots.

Rookie Renardo Green flashed but also showed his lack of experience at times, but as a second-round pick, his roster spot is likely secured. With the rest of the competition at hand, former starter Ambry Thomas had a rough game again, missing a couple of tackles and committing a holding penalty. Rock Ya-Sin, on the other hand, had a phenomenal game.

With reports that Ambry Thomas suffered a break in his forearm, it is unlikely Thomas will have a place on the 49ers 53-man roster, either with a roster cut when healthy or by being moved to IR.

Ya-Sin's Grade: A-/Green's Grade: B/Thomas's Grade: F