SEATTLE -- On a personal level, the decision to fire defensive coordinator Ken Norton Jr. had to be brutal for Pete Carroll.

The Seattle Seahawks coach is known for loyalty to his assistants and has long had a particular affinity for Norton, once calling him one of the favorite people he's worked with during his coaching career. The two go back to the mid-90s, when Norton was an All-Pro linebacker for the San Francisco 49ers while Carroll was their defensive coordinator. Norton worked under Carroll for 15 of the past 18 seasons dating back to their time at USC.

In that sense, Seattle firing Norton this week, along with defensive passing-game coordinator Andre Curtis, was mildly surprising.

In every other sense, it was not.

The Seahawks' defense was good at times during Norton's four-year tenure. But two of the best stretches followed awful starts to each of the past two seasons, when Seattle allowed yards at historic rates early before turning things around. It was not consistently great over any of those four seasons, never ranking inside the top 10 in points allowed or top 15 in yards allowed.

In fairness to Norton, he didn't have the same level of talent that predecessors Kris Richard, Dan Quinn and Gus Bradley did during the Legion of Boom days. And while Seattle's defense was part of the problem in 2021, especially early, it's hard to argue it was the biggest reason they finished 7-10 and missed the playoffs for only the second time in the past 10 seasons.

No one expected status quo after a season in which the Seahawks suffered their most losses in more than a decade.

Now the search is underway for their fifth defensive coordinator of Carroll's tenure.

A source told ESPN's Jeremy Fowler that they've requested an interview with Denver Broncos DC Ed Donatell. The other reported candidates are Seahawks defensive line coach/assistant head coach Clint Hurtt (per The Seattle Times), Chicago Bears DC Sean Desai (per The Athletic) and Joe Whitt Jr. (per the NFL Network), the Dallas Cowboys' defensive passing game coordinator and secondary coach.

Before a look at each candidate, here are three questions worth considering:

What role did Jody Allen have in the Norton and Curtis decisions? Their firings came days after Carroll and general manager John Schneider met with Allen, who's been the team's de facto owner since her brother Paul Allen passed away in 2018. It's believed that the major shakeup to Carroll's staff following the 2017 season was largely at Paul Allen's behest. It's fair to wonder what influence Jody Allen had on these changes.

How appealing is the Seahawks' DC job? It depends on the coach. Anyone that Carroll hires would be running Carroll's defense for the most part. A more established coordinator who's had success running his own scheme would presumably be disinclined to adopt someone else's. To some candidates, though, the Seattle job would carry plenty of appeal. There are the usual questions about which free agents (Quandre Diggs, D.J. Reed, Al Woods) and under-contract players (Bobby Wagner) will be back.

But between what they already have, who they'll re-sign and who they may add in free agency with their ample cap space, there should be enough talent to make it far from a rebuilding effort. And it may be equally attractive to prospective DCs that the Seahawks have a quarterback and offense that should be able to do their part, assuming Russell Wilson isn't traded.

What schematic changes might Carroll have in mind? Long gone are the days when the Seahawks would run pretty much the same defense, knowing they were good enough to execute even if opposing offenses knew what was coming. They've done things differently in recent seasons. In 2019, it was an unusually heavy dose of base personnel. In 2021, they frequently used what was essentially a five-man defensive line. They also played more man later in the year, according to Reed, which helped curb all the yards they were allowing in soft zones early on.

Point being: Carroll has been adapting his defense. Whatever changes he makes will likely be geared towards generating more pressure and turnovers. They were tied for 22nd in sacks last year and 25th in takeaways.

Here's a look at the four reported candidates:

Ed Donatell. The 64-year-old Donatell has a long history with Carroll that began in 1983 at University of the Pacific. They also spent four seasons together (1990-94) with the Jets. Donatell coached defensive backs in both of those stops, which has been his primary position group throughout his coaching career. He worked closely with Broncos DBs during his three seasons in Denver, where he ran coach Vic Fangio's defense.

The Broncos allowed the third-fewest points of any team in 2021. That seems indicative of strong coaching when you consider the personnel challenges they dealt with between the Von Miller trade, Bradley Chubb only playing seven games and numerous injuries to their inside linebackers.

Clint Hurtt. The only in-house candidate of the four, the 43-year-old Hurtt has spent the past five seasons on Carroll's staff. He previously coached outside linebackers with Chicago. As disappointing as the Seahawks' pass rush was in 2021, their defense was strong at stopping the run, allowing the second-fewest yards per carry in the NFL.

Could the Seahawks go with a dual-coordinator role in which Hurtt is in charge of their run defense while someone else handles the pass defense? They had that arrangement on offense during their Super Bowl years between Darrell Bevell and Tom Cable. Per Fowler, Hurtt is also in the mix for the DC job at the University of Miami, his alma mater.

Joe Whitt Jr. The 43-year-old Whitt doesn't have history with Carroll but did spend parts of the past two seasons working under Carroll disciple Dan Quinn. Whitt was the Atlanta Falcons' defensive passing game coordinator and secondary coach in 2020, Quinn's last year as Falcons head coach. Whitt followed Quinn to Dallas last offseason after Quinn was named the Cowboys' DC. Quinn coordinated Carroll's defense in 2013 and '14 and has continued to run a similar scheme, which provides some built-in familiarity with Whitt. Carroll has to like what Dallas did this past season in leading the NFL in interceptions and takeaways.

Sean Desai. He also has no direct experience with Carroll, having worked in the college ranks before he began his nine-year run with the Bears in 2013. He is coming off his first season as a defensive coordinator at any level. The 38-year-old Desai was Chicago's safeties coach for two seasons (2019-20) before they elevated him to DC last year. The Bears ranked 22nd in points allowed last season and sixth in yards allowed.

According to the team's website, Desai is the NFL's first Indian-American coordinator. He earned his doctorate in educational administration in 2018 from Temple, where he served as an adjunct professor in 2009 and '10.