Since the NFL introduced the salary cap in 1994, team owners haven't been shy about changing head coaches. There's been an average of seven changes per year, and that number has held up for more than two decades.

There have been 43 changes since 2011, which is slightly more than that seven-per-year mark.

Owners have changed coaches so often that the list of legitimate candidates continues to dry up. Last year, six offensive assistants got head-coaching jobs and the Titans signed then-interim Mike Mularkey to a three-year deal.

So who are the candidates to keep an eye on when head-coaching jobs open at the end of the season?

First, keep an eye on the trend of offensive assistants getting top jobs. That likely won't go away, and there are a several offensive coordinators who will get interviews.

Second, don't look to the collegiate level. It appears unlikely that any college coaches will be in the mix for NFL jobs. Notre Dame's Brian Kelly had been on the radar of some NFL owners in recent years, but the Fighting Irish went just 4-8 this season. UCLA's Jim Mora has been an NFL head coach twice before, but the Bruins went 4-8 too.

Here are 16 candidates who could be head coaches in 2017, in no order: