RENTON — The Seattle Seahawks defense is back, that much became clear over the past three games as they held the Arizona Cardinals, San Francisco 49ers and most recently — and impressively — the Philadelphia Eagles to each team’s lowest point and yardage totals of the season.

And there are plenty of reasons to explain Seattle’s defensive improvements. From the team’s improving health — most notably the return of middle linebacker Bobby Wagner from a five-game absence and the improved health of strong safety Kam Chancellor, who limped through the first half of the season before missing two games — to the now famous clear-the-air team meeting that occurred before the Arizona game.

What stands out most to Seahawks head coach Pete Carroll about his defense is not just having all of his players back, aside from defensive tackle Brandon Mebane, but how much better individuals can function when the team around them is at full strength.

“I think it’s more the chemistry of the guys playing together and their sense for one another and playing familiar spots and all that kind of stuff has really paid off,” Carroll said.

As many players as Seattle returned from its championship defense, several key players did leave in the offseason, including cornerback Brandon Browner, cornerback Walter Thurmond, defensive ends Chris Clemons and Red Bryant and defensive tackle Clinton McDonald.

Those departures meant working new players into the mix or adding to other players’ work load. Free-agent defensive tackle Kevin Williams had to fill a different role when Mebane was injured. Second-year defensive tackle Jordan Hill and second-year cornerback Tharold Simon have bigger roles. And there is more playing time for defensive ends Cliff Avril and Michael Bennett. Sorting all of that out takes time, and that process was certainly hindered by the midseason rash of injuries.

That’s where the camaraderie factor Carroll mentions come in. And it’s why he is encouraged by what he is seeing now. Both from the players who have been around for a while like Chancellor, free safety Earl Thomas and cornerback Richard Sherman, and from the young players taking on new roles this season.

“Our guys have been together a long time now, even though they’re still only four years old in the league or whatever, they’ve still been together a long time and done a lot of stuff together,” Carroll said. “So they’re coming together and they’re learning one another and they’re learning what it takes to play at a really high level.”

And what the Seahawks have done in the past three games, holding their opponents to a total of 507 yards and 20 points, has certainly been impressive.

Heading into the Cardinals game, the Seahawks ranked third in the league in yards allowed at 306.1 per game, and 12th in points allowed with 21.5 per game. It took Seattle just three games to lower those numbers to 274.5 yards per game, which ranks first, and 18.1 points, which ranks second in the league. The Seahawks have a good shot at bettering last year’s league-leading number for yards allowed (273.6 per game), though they’ve already allowed four more points than they did all of last season when they gave up 14.4 points per game.

Over the past nine seasons, only three teams have allowed fewer yards over a four-game span than what Seattle accomplished. Though the lower totals (422 by the 2009 Giants, 494 by the ’11 Texans and 497 by the ’09 Jets) were all posted by teams facing opposition with losing records, while the Seahawks just dominated three teams that had a combined .758 winning percentage.

The key, of course, is to maintain this level of excellence, or something close to it, going forward. What the Seahawks have done of late is impressive, but it won’t mean much if they falter down the stretch or in the playoffs. The perhaps encouraging news for the Seahawks is when they had a midseason swoon last season, giving up more than 200 rushing yards in back-to-back games, they were able to maintain a high level of defensive play throughout the rest of the season once they fixed things.

“Anybody can do it sometimes,” Carroll said. “The challenge is, can you do it consistently and find a way to always be on your game? That’s the tremendous challenge of the coaching staff and the team and the team leaders and all of that so we’re trying to figure that out and see if we can do it one more time.”

John Boyle covers the Seattle Seahawks for the Everett Daily Herald. He can be reached at jboyle@heraldnet.com.