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A coaching tree is similar to a family tree except it shows the relationships of coaches instead of family members. There are several different 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 (see Len Pasquarelli article). Each branch of the tree shows a relationship between one coach and their predecessor. The relationship shown on the below trees are of an assistant coach to a head coach. The former assistant branches out from the head coach that they used to work for. The tree examples below only show the relationship of former assistant coaches to their former head coach. In several cases, an assistant coach learns a general philosophy from their head coach. Coaching trees can also show a philosophical relationship between an assistant and a former head coach who mentored them (see Tony Dungy below). In the current NFL, 31 active head coaches trace their roots back to three main prominent Head Coaches: Bill Walsh, Bill Parcells, and Marty Schottenheimer (See Graphic Below).
In 1998, half of the active head coaches in the National Football League could be traced to Bill Walsh and Tom Landry. Of those 15 coaches, four (plus Walsh and Landry) had coached a Super Bowl winning team.
Philosophical Tree Connections 
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:
- Norv Turner: Most recently Turner worked as an Offensive Coordinator under Mike Nolan in San Francisco. However, Nolan previously worked under Turner when he was the Head Coach with the Redskins as a Defensive Coordinator 1997-1999. Also, before getting his first head coaching job with the Redskins in 1994, Turner worked under both John Robinson in Los Angeles and Jimmy Johnson in Dallas. Turner article
- Wade Phillips: Coached under Marty Schottenheimer, but primarily learned his philosophy from his father, Bum Phillips. Phillips article
- Jon Gruden: Worked under Mike Holmgren in Green Bay. Holmgren/Gruden article
- Tony Dungy: Is listed above as part of the Schottenheimer coaching tree. 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. Dungy article
- Todd Haley: Coached under Bill Parcells and learned his philosophy from him for many years before joining Ken Whisenhunt in Arizona, in 2007.
- Steve Spagnuolo: While Spagnuolo is credited under Tom Coughlin and Bill Parcells tree, he studied and learned much of his style and system during his tenure in Philadelphia under Jim Johnson and Andy Reid. Spagnuolo took Johnson's style of play to New York where he gained national attention for his scheming and personnel packages that helped shut down New England in the Super Bowl, one of the biggest upsets in NFL history. He then took that defense to St. Louis.
- Jack Del Rio: He worked under Marvin Lewis on the Ravens' defensive staff. However, Del Río got his coaching start from Mike Ditka in New Orleans, and then worked as Defensive Coordinator under John Fox in Carolina before being hired by Jacksonville in 2003.
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 NFL Coaching Tree By Brad Oremland
- 'An offense by any other name...' By Len Pasquarelli
- Dungy’s legacy could be coaching tree By Don Pierson
- Bill Walsh planted the ultimate coaching tree By Nancy Gay