Nothing about the 49ers defense was exotic or unexpected last season.
They hardly rotated their safeties and almost never disguised their coverages. If the middle of the field was open before the snap, it most likely was open after the snap as well. And if a defender blitzed, usually you could see him coming from a mile away. Which means good quarterbacks could figure out what the 49ers defense would do before the play even started.
It's hard to think of examples from last season when defensive coordinator Nick Sorensen called a coverage that confused or quarterback, or called a blitz that actually worked. Now he's the special teams coordinator for the Dallas Cowboys.
His replacement is Robert Saleh, who's a top-five defensive coordinator in the NFL. You can bet that his defense will keep opposing offenses off balance.
For starters, his defense will disguise its coverages. That means the safeties will move after the snap, so quarterbacks won't immediately know what coverage the 49ers are running. That will force him to hold the ball a beat longer than normal.
In addition, Saleh will disguise his blitzes. Meaning he won't rush the same players every time. Sometimes, he'll blitz a linebacker. Other times, he'll blitz the nickelback. Other times, he'll blitz a nickelback and drop a defensive lineman into coverage and rush just four players. We never saw the 49ers do this under Sorensen.
Instead, he almost always rushed four defensive linemen, and Nick Bosa would get double-teamed. This year, Saleh will force opposing offenses to account for more than just Bosa.
Thank goodness Saleh is back.