Seattle Seahawks center Max Unger and punter Jon Ryan have some historical perspective on the frantic roster building they witnessed when John Schneider was hired as general manager and Pete Carroll as head coach after the 2009 season.

About $52 million in salaries were slashed from the payroll, clearing the books and the runway for Schneider and Carroll to construct a championship team. Where do Unger and Ryan fit in the process? They are the only players on the current 53-man roster that predated the arrival of the current Seahawks’ braintrust.

Ryan was signed as a free agent in 2008. Unger was a second-round pick in 2009.

One other player, defensive tackle Brandon Mebane, is on injured reserve and was selected in the third round of the 2007 draft.

Only five other players have been with the Seahawks since 2010: tackle Russell Okung (first round), safeties Earl Thomas (first) and Kam Chancellor (fifth), running back Marshawn Lynch (trade, Buffalo Bills) and long snapper Clint Gresham (waivers, New Orleans).

By contrast, Seattle’s opponent in Super Bowl XLIX, the New England Patriots, has 12 players on the current roster that arrived prior to 2011. Of course, Patriots head coach Bill Belichick’s philosophy of roster building has been consistent since he was hired to replace Carroll in 2000.

In reality, there are similarities in the the two plans: build from within through the draft and with undrafted free agents; bolster the depth with available players that fit; and, rarely enter the usually chaotic atmosphere of unrestricted free agency that this year begins March 10 and sees stratospheric contracts given to players in the first 10-14 days of the signing period.

Each team has dabbled, but not very often.

The Seahawks and Patriots each have only three unrestricted free agents on their roster, and most didn’t receive blockbuster deals.

Seattle signed defensive ends Cliff Avril and Michael Bennett, as well as defensive tackle Tony McDaniel. New England added wide receivers Danny Amendola and Brandon LaFell along with Seattle cast-off cornerback Brandon Browner.

Patriots cornerback Darrelle Revis had been cut by Tampa Bay, so he is not officially considered unrestricted, and he has a contract that will likely require restructuring if he is to return to the Patriots in 2015.

No matter how successful teams are, mistakes are made.

What’s important is recognizing them and making the necessary corrections.

The Seahawks faced a major decision earlier this season after giving up three draft picks, including one in the first round, and giving a large contract extension to wide receiver Percy Harvin. The Seahawks acquired Harvin via trade from the Minnesota Vikings in March 2013.

Harvin rarely played that season, and was then traded to the Jets in October 2014, two days before the Seahawks lost to the St. Louis Rams to drop their record to 3-3. Since the deal, they have lost just once.

Explained Schneider, “We took a shot for a highly explosive player. For a number of different reasons it didn’t work out and we knew that we had to resolve that situation as quickly as we could so that we could just move forward as a football team.”

What’s also notable are the number of undrafted free agents on each team’s roster, whether they were home-bred or entered the league with another team. The Seahawks have 24 undrafted players on their 53-man roster, 12 of whom were originally signed by Seattle. Seven of those 12 made the team as rookies and have never been cut. Of the other five, one is the aforementioned Bennett, who signed with Seattle in 2009, and came back in 2013 after playing for the Buccaneers.

Asked about their success with undrafted players, Schneider said, “I think it’s a combination of good coaches, good teachers and good acquisitions and being able to identify guys that have a legitimate chance of coming in and making your roster.”

The most notable undrafted Seahawks producers are wide receivers Doug Baldwin and Jermaine Kearse.

New England has 19 undrafted players on its roster, including six they originally signed.

The Patriots have 18 picks from the first three rounds on their roster, four of whom were first selected by other teams. Six are first-round choices: defensive tackle Vince Wilfork (2004), safety Devin McCourty (2010), tackle Nate Solder (2011), defensive end Chandler Jones and linebacker Dont’a Hightower (2012) and Revis (N.Y. Jets, 2007). Linebacker Jerod Mayo (2008) and defensive lineman Dominique Easley (2014) are on injured reserve.

The Seahawks have 14 choices from the first three rounds, with three beginning on other teams.

Seattle’s first-rounders are Okung, Thomas, guard James Carpenter (2011), linebacker/defensive end Bruce Irvin (2012), defensive tackle Kevin Williams (Minnesota, 2003) and Lynch (Buffalo, 2007).

While the first round has all the hype, it’s notable that 12 of the 92 players that will dress for Sunday’s game came from that round.

While the personalities of Carroll and Belichick are wildly divergent, it’s clear their organizational goal is to find like-minded players that simply love to play the game.

Belichick verbalized the basics of that approach at a symposium in Boston in 2013. He said, “The big thing I’d say we look for, which would try to differentiate the players for us, are players with passion; guys that really love football. As we all know from our jobs, if you love what you’re doing you don’t feel like you’re working. If you don’t like what you’re doing, then every step of the way is just painful torture. We don’t want people who are in football because of the lifestyle it brings or the opportunities or rewards from it. We want people who are in our business because they love doing it.”

Schneider was asked recently if he could have envisioned this much success so soon.

“That’s a really good question,” he said. “You know what, I think we don’t necessarily view it that way. It’s a daily thing. We are so focused and consumed about getting better in every area on a daily basis that it has just built like that over the years. I know you guys have heard me talk about being a consistent championship-caliber team. And with that comes really tough decisions, like, every day. Obviously, it’s what you strive for.”

Howard Balzer is based in St. Louis and is a selector for the Pro Football Hall of Fame. He has covered the NFL for more than three decades.