New Eagles coach Nick Sirianni may not be the youngest coach in the NFL, but the coordinating staff he assembled is, and in terms of positional experience, they have the least amount in the league.

The rest of Sirianni’s staff is also very young, and in some cases inexperienced. The 39-year-old does have some veterans in key spots, but the first-time coach opted not to have at least one prominent assistant in a leadership role.

He clearly valued familiarity. In Jonathan Gannon and Shane Steichen, Sirianni chose defensive and offensive coordinators with whom he had previously worked. He also brought with him two assistants from the Colts — passing game coordinator Kevin Patullo and tight ends coach Jason Michael.

But Sirianni looked outside Indianapolis, as well. He retained two top assistants from the Eagles. He acquired four coaches — aside from Steichen, who came from the Los Angeles Chargers — from other NFL teams. And he plucked two aides from the college ranks.

If Sirianni didn’t have a prior relationship with a coach, there might have been an Eagles staff member who did. But there were also hires — for example, former Florida quarterbacks coach Brian Johnson — whom the coach and the team hadn’t met until the interview process.

The overarching theme of Siranni and his initial staff, however, is their relative youth and inexperience. Does that mean they won’t be successful? Hardly. There are reasons both could be viewed as positives.

But Sirianni and many of his coaches, particularly his coordinators, are unknowns, and their age and lack of experience in their new jobs only add to the uncertainty.

The Eagles have the youngest coaching staff in the NFL — Gannon is 37, Steichen 35, and special teams coordinator Michael Clay 29 — with an average age of 35 years. The NFL average is 47.6 years.

And of the four only Steichen has logged any time in his current position. He was the Chargers’ offensive coordinator last season and his one year gives the Eagles the least amount of collective experience in the league and is well below the average of 21.4 years.

He is also the only one out of the four to ever call plays. But Sirianni will handle that role with the Eagles.

It takes time, of course, to build resumes. Most new coaches will weigh down the average of a group, but even compared with the six other teams who hired new coaches this offseason, the Eagles are younger than the average of 46.3 years and the combined average of 10 years of experience.

» READ MORE: Ken Whisenhunt has worked with Sirianni and Steichen. He says they will earn players' respect.

Sirianni wasn’t available to interview for this story, but he did touch on the subject not long after he was hired in January. The Eagles had yet to announce his staff, but several names had been reported by the time of his introductory news conference.

“I’m looking for good coaches,” Sirianni said when he was asked if he valued familiarity over experience. “The net is cast, right? We looked at a bunch of people, of who we wanted to hire in those positions and it just kept coming back to those guys being the best candidates because of who they are as football coaches and people.”

Overall, the average age of the Eagles’ 13 top assistants is 39.9 years. Offensive line coach/run game coordinator Jeff Stoutland is the oldest at 59. Linebackers coach Nick Rallis is the youngest at 27.

Rallis is the youngest positional coach in the NFL. Clay is the youngest coordinator. Rallis worked with Minnesota Vikings linebackers for three seasons as a quality control assistant, and Clay helped out with special teams most recently with the 49ers and for one year with the Eagles, but both will be neophytes as positional heads.

Sirianni does have assistants with long coaching records. Stoutland has 37 years total. Running backs coach/assistant head coach Jemal Singleton has 20 years. Defensive line coach Tracy Rocker has 29 years. Michael has 15 years, two of them as an offensive coordinator with the Tennessee Titans from 2014-15.

But what raised a few eyebrows was that Sirianni didn’t hire a coordinator or a senior assistant with extensive expertise in that position or prior experience as a head coach.

“Of course, we thought through everything,” Sirianni said when asked in January about the possibility of bringing in a CEO-type coach to help oversee aspects of the team unrelated to play calling. “Everything was on the table as far as what you’re saying as far as being the CEO and the play-caller or just the CEO. Of course, we thought through all of that. With my expertise in offense, we just all thought that would be the best direction to go to call the plays.”

Some first-time NFL coaches have a former head coach or veteran coordinator on staff as a sounding board and to help in areas in which he might not be familiar. A veteran assistant could also add gravitas, particularly in relationships with players.

» READ MORE: Nick Sirianni's first season with the Eagles will be rough. So use the right standard to judge him.

Former Eagles coach Doug Pederson had Jim Schwartz. His predecessor, Chip Kelly, had Pat Shurmur. It’s unclear how much impact either coordinator had in those areas, but Pederson and Kelly initially cited their experiences as head coaches as reasons for the hires.

There are currently 16 NFL teams — only half — with former head coaches on staff. Sirianni wasn’t the only new coach to skip the convention. The Houston Texans’ David Culley and Detroit Lions’ Dan Campbell are the only ones with former head coaches — defensive coordinator Lovie Smith and offensive coordinator Anthony Lynn, respectively — in prominent roles.

The Atlanta Falcons’ Arthur Smith, Jacksonville Jaguars’ Urban Meyer, New York Jets’ Robert Saleh, and Chargers’ Brandon Staley — also all first-time head coaches — decided against having a former head coach on staff. But Smith and Meyer do have assistants — defensive coordinator Dean Pees and offensive coordinator Darrell Bevell — with extensive experience.

Saleh and Staley went more the Sirianni route, although their coordinators are older (42.3 and 41 years in average) and collectively have more experience, however marginal, in their respective roles (six and three years).

Ultimately, they’re just numbers. A counterargument could be made for having too much age and experience on staff. Older coaches could be resistant to change or innovation. They could have trouble relating to millennial and Generation Y professional athletes.

Andy Reid’s first staff with the Eagles has been deemed as one of the best in recent memory. Seven of his assistants would go on to become head coaches. Jim Johnson would be regarded as one of the best defensive coordinators of that era.

But many of those coaches — names like John Harbaugh, Ron Rivera, Steve Spagnuolo, Leslie Frazier, and Sean McDermott — were unknown back in 1999. Johnson, who previously failed in a two-year stint as an NFL coordinator, was a controversial choice at the time.

When the then-38-year-old Kyle Shanahan was hired as the San Francisco 49ers head coach in 2017, he eschewed having an offensive coordinator and hired a defensive coordinator (Saleh) and special teams coordinator (Rich Hightower) without positional experience.

His pass game (Mike LeFleur) and run game (Mike McDaniel) coordinators were only 30 and 34 years old at the time. The 49ers, of course, reached the Super Bowl by Shanahan’s third season in San Francisco. Saleh has since become a head coach and taken LeFleur with him to New York as his offensive coordinator and McDaniel was promoted to offensive coordinator after he left.

And for Saleh’s replacement, Shanahan tabbed linebackers coach DeMeco Ryans, who has only four years coaching experience after a 10-year NFL career, the last four of which came in Philadelphia.

Some speculated that Shanahan would bring his father, Mike — a two-time Super Bowl-winning coach with the Denver Broncos — with him to the 49ers. But for various reasons he opted not to, likely because he wanted to avoid the possibility of being overshadowed. And if advice was all he sought from his father, he could simply pick up the phone.

Sirianni can do the same with his father, Fran, who coached at Southwestern Central High in Jamestown, N.Y., or his older brother, Jay, would later follow his dad at the school, or his other older brother, Mike, who has coached Washington and Lee University for 17 years.

And if he’s looking for NFL guidance, he can always hit up past head coaches like Todd Haley, Ken Whisenhunt, Romeo Crennel, and Frank Reich for whom he has worked.

Ultimately, the onus will fall on Sirianni and the success or failure of his assistants will largely be dependent upon how he coaches. He’s young, inexperienced, and has never called plays at any level, but just because he’s in some ways a blank slate, doesn’t mean he isn’t ready for the task.

But he certainly assembled a staff with as many question marks.