They were together for only two years when Carroll was 49ers defensive coordinator in the mid-1990s and Walsh was serving as a consultant for the team after wrapping up his coaching career. But those lessons have remained vital for Carroll as he's built the Seahawks into the NFC favorite to reach the Super Bowl after a 13-3 regular season.
"Bill Walsh used to say that, it takes five years before you can really bank on the experience of being together," Carroll said. "And he referred to that as 'the reservoir of experiences that you have and that you can draw on,' so that when you're faced with adjustments and adaptations, you've been through it before. So you can swiftly make the changes.
"So four years; we're getting there. It hasn't been everybody for four years, but there's a nucleus of the guys that I think you're referring to that have been with us and they know our language so well, and they trust the background and history, and so we can make sense of things very quickly."
The Seahawks will open the postseason next Saturday when they host a divisional playoff game. It will be the first time Seattle has hosted a playoff home game beyond the wild-card round since the 2005 postseason, when the Seahawks had home-field advantage and made their only Super Bowl trip.
And the Seahawks enter the postseason with a roster mostly built through the draft, with a few free agents additions here and there. Most important is the continuity of being together for more than just one season. It's a group that has learned how to win in all settings.
The Seahawks shook a nearly 30-year drought of winning a postseason game on the road by beating Washington last January. They spent this season dispelling the notion they can't win outside of Seattle with a franchise-record six regular-season road victories. And then there is their domination at home, winning 15 of their last 16 games at CenturyLink Field.
The Seahawks may be a young team, but they are not newbies to the challenges they're about to face. They've built a trust that in turn has created confidence.
"There are a lot of subtle things you have to know about each other's games that allow you to play together," Seattle cornerback Richard Sherman said. "Now we know each other like the back of our hands and it's a lot easier. That can be said at every level."
The success of this season was not reliant on a rush of offseason free agent signings or major trades. That's not to diminish some of the moves Seattle made. Ends Cliff Avril and Michael Bennett and tackle Tony McDaniel have been important additions to one of the deepest defensive lines in the league. Linebacker O'Brien Schofield getting picked up off waivers during training camp provided needed depth early in the season, and re-signing both defensive tackle Clinton McDonald and fullback Michael Robinson after they were released at the end of the preseason were bargain decisions.
But Percy Harvin has appeared in one game all season after being the big acquisition. Harvin was sidelined by hip surgery in August and then slowed by soreness around the repaired labrum following his debut in Week 11 against Minnesota.
Veteran defensive back Antoine Winfield was signed to be the fifth cornerback, only to get beaten out for the job by Walter Thurmond, another draft pick under Carroll and general manager John Schneider.
Of Seattle's offensive starters for most of this season, nine have been with the team since the start of the 2011 season. Marshawn Lynch, Golden Tate, Russell Okung and Breno Giacomini have been with the Seahawks since Carroll's first season in 2010. The two outliers among the starters: quarterback Russell Wilson and guard J.R. Sweezy.
On the other side of the ball, the influx of signings helped Seattle's defensive line create more pressure and add enough depth for regular rotations. The Seahawks finished tied for eighth in the NFL with 44 sacks, up from 36 last season.
But the rest of Seattle's starting linebackers and secondary entering the postseason - including safety Earl Thomas, cornerback Richard Sherman and linebacker Bobby Wagner - were all draft picks selected between 2010-12.
"You're playing with guys that you just love to be around; whenever you're around guys that you like to be around it makes your job fun," Wagner said. "You can look to the guy next to you and know they're going to do their job and it makes life easier."