The San Francisco 49ers, under new defensive coordinator Robert Saleh, are installing a new 4-3 under/over-hybrid defensive system for the 2017 season. We clear up some common misconceptions surrounding the Niners’ new base defense.

Over the past six years, 49ers defensive coordinator Robert Saleh worked for some of the top defensive minds in the NFL, including Pete Carroll, Dan Quinn and Gus Bradley.

During Saleh’s tenure, all three coaches ran a similar style of defense, and the 49ers hope Saleh will be as successful implementing this defensive system in San Francisco.

The 49ers’ new defense will be a 4-3 under/over-hybrid because on the majority of base snaps, the defense will play in either a 4-3 under-hybrid or a 4-3 over-hybrid front.

These versions of the 4-3 are “hybrids” because at times, some linemen are responsible for two gaps, as opposed to the 4-3 one-gap standard. Many articles written this offseason have touched on the theme that the 49ers’ new defense will be a 4-3 defense with elements of a 3-4.

However, the new defense is also “hybrid” in that it merges the 4-3 under and 4-3 over fronts into one consistent scheme. Unfortunately, not a lot has been written about this factor, which has caused a lot of confusion and misinformation from the media regarding the 49ers’ new defensive system.

The first common misconception is the 49ers’ new base defense will only utilize 4-3 under fronts.