The Kansas City Chiefs were first in the NFL with just four rushing touchdowns allowed last season which would lead you to believe they had a good run defense. That would be wrong. The Chiefs run defense was not very good last season.
This year, they should be better.
First, Derrick Johnson and Mike DeVito are returning. Nothing against Josh Mauga, James-Michael Johnson and others who filled in at linebacker, but they're not Derrick Johnson. And DeVito, if he comes back fully from his Achilles injury, should strengthen the rotation.
Second, the Chiefs should be playing from ahead more often than they were last year, which means more passing from the opposing team. That's just optimism at this point but that should help the rushing numbers to something more respectable than 28th in the NFL.
Finally, as Matt Verderame writes, the defensive line depth should be stronger this year. Jaye Howard and Mike Catapano figure to work into the rotation this year along with anyone else that pops up during training camp. (This is where I would usually write something about someone backing up Dontari Poe but we know by now he's not coming off the field.)
These are a lot of things that "should" happen but even a run defense that ranked in the middle of the pack would make the Chiefs defense much scarier.