A coaching tree is similar to a family tree except it shows the relationships of coaches instead of family members. There are several ways to define a relationship between two coaches. The most common way to make the distinction is if a coach worked as an assistant on a particular head coach's staff for at least a season then that coach can be counted as being a branch on the head coach's coaching tree. Coaching trees can also show philosophical influence from one head coach to an assistant.
Coaching trees are common in the National Football League and most coaches in the NFL can trace their lineage back to a certain head coach for whom they previously worked as an assistant.
The phrase "coaching tree" has also grown to refer colloquially to any idea or set of ideas originated by an individual or group. For example, an individual may claim an original idiom or phrase as part of his or her coaching tree if used by another individual.
Coaching trees are becoming more prominent in today's NFL culture. They are often referenced by various media outlets, such as ESPN.
20 years later, in 2018, an ESPN article showed visually how 28 of the 32 coaches who would serve as NFL head coaches in the upcoming season were connected to head coaches Bill Parcells and Bill Belichick. The only team that wasn't profiled in this particular story was the Indianapolis Colts, who hadn't yet hired a head coach at the time of the article. The Colts later hired Frank Reich. The only three NFL head coaches who couldn't be connected to either Parcells or Belichick, according to this said article, were the following coaches: Andy Reid of the Kansas City Chiefs, Matt Nagy of the Chicago Bears, and Doug Pederson of the Philadelphia Eagles. Incidentally, both Pederson and Nagy were once former assistants under Reid before becoming head coaches. Additionally, before Reich became head coach of the Colts, he served as Pederson's offensive coordinator of the Eagles, and helped Philadelphia win Super Bowl LII. Therefore, Reich is connected to Reid through Pederson.
In October 2018, The Washington Post published their own article about NFL coaching trees, mapping out the roots, influences and origins of every active NFL head coach.
Coaching tree examples (shown visually below) for Bill Walsh & Marty Schottenheimer:
Coaching trees can also show a philosophical relationship between a mentor head coach and their protégé. Below is a list of current and former head coaches and who they primarily developed their philosophy under:
Tony Dungy: Dungy is listed above as part of the Schottenheimer coaching tree and was a Defensive Coordinator under Dennis Green. However, Dungy attributes most of his coaching style from tutelage under Chuck Noll. Noll learned much of his own philosophy from Paul Brown. Noll coached Dungy as a player and also gave him his first NFL position as the defensive backs coach of the Pittsburgh Steelers. Dungy later became the defensive coordinator for the Steelers.
Additionally, many college football coaches worked as assistants for head coaches on the tree. For instance, Bill Belichick can claim Kirk Ferentz, Nick Saban, and Charlie Weis as descendants of his tree, though they are not included in the graphic above.
Bum Phillips coached under Gillman with the Oilers, and was chosen by Gillman to succeed him upon Gillman's stepping down from the head coaching job of the Houston Oilers.
The Bill Belichick coaching tree is a far-reaching one. During Belichick's long-tenured career as an NFL head coach, 17 assistant coaches under him have gone on to become head coaches in both the NFL and college. They then sprouted their own trees, leading to over 100 total offshoots, which include 13 active NFL head coaches.