RENTON — The moment that may have best defined the Seattle Seahawks’ stuttering start to the 2015 season came in the final moments of regulation of Seattle’s opening game.

The Seahawks, after falling behind, rallied to take a 31-24 lead over the St. Louis Rams. All Seattle needed to do to open its season with a victory was prevent the Rams from marching into the end zone from midfield in the game’s final minute.

But on third-and-five from the Seattle 37-yard line, Seahawks strong safety Dion Bailey was caught flat-footed and stumbled, leaving St. Louis tight end Lance Kendricks wide open for the game-tying touchdown with 59 seconds remaining. The Rams went on to win 34-31 in overtime.

Bailey, an undrafted free agent, was only starting that game because usual starter Kam Chancellor was in the middle of a holdout. Chancellor eventually returned in Week 3, but it wasn’t enough to prevent the Seahawks’ slow start. Seattle began the season 2-4, a stretch filled with fourth-quarter collapses and defensive miscommunication, and that start may have cost the Seahawks their chance at reaching a third straight Super Bowl.

But Seattle will have no such issues this season.

This year the Seahawks have Chancellor ready and available from the start, and that could make all the difference.

“It’s a big boost for us,” Seahawks coach Pete Carroll said. “He’s a great leader, he’s always been a great leader. He’s a terrific player as well. The combination of what he brings and the play of the field is just really special to us and we’re thrilled to have him.”

Chancellor was a surprise holdout when training camp began last summer, dissatisfaction with his contract being the catalyst. Chancellor’s holdout lasted the entirety of training camp, preseason and the first two games of the regular season.

Without its captain and enforcer — Chancellor is the player who puts the “boom” in the Legion of Boom — Seattle’s vaunted defense looked confused and disorganized. The Seahawks lost the two games Chancellor missed, then dropped two more as Chancellor went through the equivalent of his own training camp on the fly over the ensuing month. In all four of those defeats Seattle was unable to hold onto a fourth-quarter lead.

But once Chancellor got his feet under him, Seattle’s defense reverted to its dominant self. Through the first six games the Seahawks allowed 20.1 points per game, then during the final 10 that number fell to 15.1, including a minuscule 11.0 over the final five. Seattle ended up leading the NFL in scoring defense for the fourth straight season.

It’s the defense that ended the season, rather than the one that started it, that Seattle will have when the season opens Sunday against the Miami Dolphins.

“It’s great,” Seahawks cornerback Richard Sherman said about having Chancellor back. “I’m sure the D-line is happy, he makes a lot of checks with the D-line. He brings his physicality, his menace to the defense. So it’ll be great. It’ll be great to have everybody on board.”

Chancellor received no concessions from last year’s holdout as he’s still playing under the four-year, $28 million contract he signed in 2013. Yet he chose not to hold out this year and has has been a model citizen, saying all the right things.

“I learned that this is a new year,” Chancellor said about his experience with the holdout. “I learned that this is a business, this is the NFL. But more importantly, it’s about a brotherhood. We started a brotherhood here and you know, we’ve got to continue what we’ve started with that. That’s the important thing.”

All has been forgiven by his teammates, too. Chancellor was the team’s defensive captain in 2014, a title he relinquished to linebacker Bobby Wagner last year during his holdout. However, when the players voted for captains this year, Chancellor was restored to the captaincy.

“I think no one’s ever lost faith in him,” defensive end Michael Bennett said.

“Kam is the best at what he does,” Bennett added. “He’s here, he’s an enforcer, he’s everything, he’s the captain of our team. He does everything right. He’s just a special talent and we’re lucky to have a teammate like him.”

How does having Chancellor with the team from the start affect Seattle’s defense?

“It’s just getting on the same page with the camaraderie, getting on the same page on the defense with the calls and the checks,” Chancellor said. “Just that energy from the beginning is going to be a bit different because we have all the pieces here. It all comes down to having all the pieces in the machine, the machine can’t work without certain pieces. So you’ve got to have everybody together, and that’s what we have now. It feels good, it feels natural, we’re ready to go.”

The moment last season when it became crystal clear just what the Seahawks were missing during Chancellor’s holdout came in Week 4 against the Detroit Lions.

There was less than two minutes remaining, Seattle was clinging to a 13-10 lead, and the Lions were driving for the go-ahead touchdown. Detroit’s Calvin Johnson caught a pass and was lunging for the goal line when Chancellor punched the ball out of Johnson’s arm from behind, with the ball going through the end zone for a touchback. That play prevented the Seahawks from falling to 1-3 and may have saved Seattle’s season.

And with Chancellor in the fold from the start, this year the Seahawks won’t have to wait for him to make his presence felt.

For more on the Seattle sports scene, check out Nick Patterson’s Seattle Sidelines blog at www.heraldnet.com/tag/seattle-sidelines, or follow him on Twitter at @NickHPatterson.