COLLEGE PARK, Maryland — When Jay Gruden was named head coach of Washington’s NFL franchise in 2014, he set out to construct a winning coaching staff.

To do that, he drew on pre-existing relationships in the “coaching social network” he established during his decade as an assistant coach under his brother Jon Gruden in Tampa Bay and Marvin Lewis in Cincinnati, a Capital News Service social network analysis found.

In the NFL, who you know often matters as much as what you know, with coaches demonstrating a strong preference for familiar people. It’s not unusual for one coach to work with another coach on multiple teams, creating a complex web of connections that spans generations.

For Jay Gruden, some parts of his coaching web have proved more important in filling open jobs in Washington. To build his staff — and replace assistants who departed for bigger jobs elsewhere — he has drawn more heavily on the network he established working for his brother’s Buccaneers between 2002 and 2008 than the network he built as an assistant with the Bengals under Lewis between 2011 and 2013, the analysis found. In fact, he hasn’t brought anyone from Lewis’ Bengals staff to Washington.

To do the analysis, Capital News Service built a dataset that included every coach and assistant who has ever worked in the NFL with Jon Gruden and Lewis. We then selected everyone from that list who later became an NFL head coach — 13 people, including Jay Gruden, Sean McVay and Kyle Shanahan — and added all of their NFL colleagues to the dataset.

Here are five other interesting things we found looking into the web of connections around Jon Gruden and Lewis.

1. Jon Gruden and Lewis have had a lasting impact on the league as mentors.

Successful coaches create opportunities for their top assistants to land head coaching gigs elsewhere.

Nine people who worked for Jon Gruden during his four years as head coach in Oakland and Tampa Bay later became head coaches. This includes Shanahan (San Francisco 49ers), Raheem Morris (formerly Tampa Bay Buccaneers), Sean McVay (Los Angeles Rams), Marc Trestman (formerly Chicago Bears), Bill Callahan (formerly Oakland Raiders), Gus Bradley (formerly Jacksonville Jaguars), Mike Tomlin (Pittsburgh Steelers) and Rod Marinelli (formerly Detroit Lions).

The visualization below shows the network of relationships between Jon Gruden, those nine people — and every assistant coach any of them worked with. The dense, interconnected nature of this network is striking, showing a surprising number of assistant coaches who worked with each other on different teams.

If you’ve never seen a social network visualization before, here’s how to interpret it (and subsequent visualizations in this story).

Each dot is a person. Bigger dots are more important parts of the network, as measured by a statistic called “centrality.” Head coaches are the biggest, with lots of common connections. Medium sized circles are the most important assistants, people who show up repeatedly on the staffs of several head coaches. The smaller dots are less important people.

Each line is a connection between two people. People who have worked together for many years have a stronger tie and, thus, a thicker line.

The colors identify “communities” in the network, clusters of people with lots of overlapping connections between them, and fewer connections to other parts of the network. Jay Gruden and McVay (offensive coordinator under Jay Gruden in Washington) have a lot of overlapping connections, which puts them in the same red-colored community.

Five people who worked for Lewis have gone onto head coaching gigs in the NFL: Jay Gruden, Mike Zimmer (Minnesota Vikings), Hue Jackson (Cleveland Browns), Vance Joseph (Denver Broncos) and Leslie Frazier (formerly of the Minnesota Vikings).

2. Latching onto a veteran coach can help inexperienced assistants move up the ranks.

The progression of McVay from an assistant coach to offensive coordinator to head coach illustrates how a coach’s network influences his NFL career.

Jay Gruden and McVay first worked together in Tampa Bay in 2008, as coaching assistants. In 2009, after the Buccaneers fired Jon Gruden, Jay Gruden and McVay worked for the United Football League’s Florida Tuskers as offensive coordinator and tight ends coach, respectively.

In 2010, McVay joined Washington’s coaching staff when Mike Shanahan became head coach. He worked under offensive coordinator Shanahan, who also spent time under Jon Gruden’s Buccaneers, but left before McVay arrived. When Jay Gruden took over for Mike Shanahan in 2014, he promoted McVay from tight ends coach to offensive coordinator.

In Washington in 2010, McVay first worked with then-quarterbacks coach Matt LaFleur. He became McVay’s offensive coordinator in Los Angeles when McVay took the reins this year. LaFleur worked with three different head coaches in the network we examined in three different cities — McVay (Washington, L.A.), Shanahan (Washington, Atlanta) and Morris (Washington, Atlanta).

3. Relationships help fired coaches get back on their feet.

Joe Barry, who has held NFL defensive coaching positions for most of the last two decades, has deep ties to the head coaches that make up the extended Jon Gruden network. These connections helped Barry get back to the league after the Detroit Lions fired him as defensive coordinator after the team’s winless 2008 season.

In 2009, he returned to Tampa Bay as linebackers coach under new head coach Raheem Morris. They had both worked together in Tampa Bay from 2002-2005 under Jon Gruden. Barry was one of the most important pieces of the network we examined, with ties to eight head coaches. He served as Jay Gruden’s defensive coordinator in Washington for two years before being fired.

Greg Olson also used the Jon Gruden coaching network to get a new job after being fired from Oakland as offensive coordinator in 2014. He caught on with the Jacksonville Jaguars as offensive coordinator in 2015 under head coach Gus Bradley, who he worked with in Tampa Bay in 2008. Bradley and Olson were both fired in 2016. This year, Olson signed on with an old Tampa Bay colleague — McVay — as quarterbacks coach in Los Angeles.

4. One way to acquire lots of connections is to stay in one spot for a long time, as head coaches come and go.

It may seem obvious, but the longer an assistant stays in the NFL, the more connections they typically acquire. We found that some of the most connected people in our network — the ones with the most ties to different head coaches — were people with long tenures in the league.

Danny Smith landed his first job in the NFL as a special teams coach was with the Philadelphia Eagles in 1995, where he worked with offensive coordinator Jon Gruden and Callahan, the offensive line coach. He moved to Detroit, then Buffalo, before settling in Washington from 2004-2012, where he worked for three different head coaches and assistants Shanahan, McVay and Morris. He later moved to Tomlin’s staff in Pittsburgh, showing that good special teams coaches are never lack for work.

Richard Mann, a veteran wide receivers coach who started in the NFL in 1982, also exemplifies the idea that longevity helps build connections. He has direct ties to 11 of the 15 coaches in the data set we built. He established most of his ties to Jon Gruden’s coaching network while working in Tampa Bay from 2002-2009. He also has crossover ties to Lewis’ coaching network, formed when he worked with Lewis on the Baltimore Ravens’ staff in 1997 and 1998.

5. Marvin Lewis keeps his people for a long time.

Lewis became the Bengals head coach in 2003, and he’s earned a reputation for low staff turnover. When his assistants leave, it’s usually because of a promotion to a better job elsewhere, or retirement. He rarely fires people.

In the visualization below, the orange relationship lines between Lewis and his assistants are thick because they spent so many years working together.

Cincinnati assistants like Darrin Simmons (special teams), Paul Guenther (defensive coordinator) and Jonathan Hayes (tight ends) have all been on Lewis’ staff for 14 years, with little worry about job security. If an assistant sticks to a loyal coach who is unlikely to get fired — like Lewis — he doesn’t have to worry about losing his job.

The lines connecting Jay Gruden to the network of Cincinnati assistants are much thinner, indicating weaker ties. It’s notable that in Washington, he hasn’t hired anyone from Lewis’s Cincinnati staff.