By most objective measures, the Seattle Seahawks’ 2016 season was a success. They went 10-5-1, won the NFC West title, and advanced to the Divisional round of the playoffs. A lot of teams would love to have that kind of year.

However, the Seahawks were merely good, not great, which feels like a disappointment after a string of dominant performances. The core team that went to two straight Super Bowls (and won in 2014) is largely intact, but there are some cracks starting to form in the foundation.

While the pieces are in place to make another run at the playoffs in 2017, what happens to the Seahawks after that is something of a mystery. Pete Carroll and John Schneider will be entering a transition period soon, and their big challenge will be keeping the team’s contention window open while Russell Wilson is still in his prime.

What went wrong for the Seahawks in 2016

The offensive line was a fatal flaw, ranking as Pro Football Focus’ worst in the NFL. The unit let Wilson get sacked 41 times. Their starting left tackle, George Fant, literally hadn’t played football since Pee Wee and it showed.

The running game struggled to adjust without Marshawn Lynch — Christine Michael, who got cut before Thanksgiving, led the team with a paltry 469 rushing yards, while Thomas Rawls never looked the same after breaking his ankle last year. Injuries depleted the secondary, most notably losing Earl Thomas to a broken leg late in the season. Watching Matt Ryan and the Atlanta Falcons light up Seattle’s defense in the playoffs was a stark reminder of how important Thomas is.

And for the most part, the Seahawks made the right moves in the offseason to shore up their weaknesses. They signed Eddie Lacy in free agency to bolster the run game. They brought in Luke Joeckel and Oday Aboushi to give the offensive line some fresh faces. They attacked defensive depth in the draft, selecting three safeties, a cornerback, and two defensive tackles (including second-rounder Malik McDowell). They kept Richard Sherman despite fielding trade offers for most of the spring.

On paper, this looks to be a good team once again. With Thomas coming back healthy, the defense should be much improved. The offensive line pieces they brought in couldn’t possibly be worse than last year’s group. And, of course, they still have Wilson. Despite struggling through injuries last year, a franchise quarterback is the most valuable asset in football, and as long as Wilson is in his prime, the Seahawks will have a leg up on most teams.

In short: The Seahawks should be playoff contenders once again. They did make at least the Divisional round in five straight seasons, after all. But the long-term future looks cloudy, especially when it concerns the heart and soul of the team: The Legion of Boom, Seattle’s group of defensive backs that have defined the Carroll era.

What’s the Legion of Boom’s future?

Led by Richard Sherman, Earl Thomas, Kam Chancellor, and a host of supporting cast members, the Legion of Boom became famous for their hard-hitting play and colorful personalities. They reached their peak in Super Bowl 48, smashing Peyton Manning and the Denver Broncos en route to a 43-8 rout and the franchise’s first-ever Lombardi Trophy.

Although that was only three years ago, the group is getting up there in age, and changes could be afoot in the near future.

All good things in football eventually must end. The Greatest Show on Turf (the Rams’ high-flying offense of the early 2000s) couldn't last forever, and neither could the Purple People Eaters (the Vikings’ fearsome defensive line from the 1960s). Players get older, contracts get expensive, and eventually there’s no choice but to break up the band. Things will be no different for the Legion of Boom.

Let’s take a look at Sherman, who was on the trade block this offseason after ruffling feathers in a feud with the local media. He also got some negative attention for jawing with defensive coordinator Kris Richard on the sidelines.

Although he’s sticking around this year, he carries a cap hit of $13.2 million in 2018, according to Over The Cap. Sherman also turns 30 next year, and cornerbacks are notorious for not aging gracefully. Look no further than Darrelle Revis to see how fast an elite cornerback can fall off. Cutting Sherman in 2018 would save the Seahawks $11 against the cap.

Schneider and Sherman were unusually candid about the trade rumors, with the GM telling media that “what you’ve seen in the news lately is real” and Sherman telling The MMQB that there’s “no bad blood” over the trade talks. Both sides are playing nice for now, but it seems pretty obvious that they’re preparing for a divorce.

Then there’s Chancellor, who is the same age as Sherman and set for free agency next year. Would the Seahawks be willing to give another long-term contract to a soon-to-be 30-year-old safety? Seattle wasn’t shy about stocking up on safeties in the draft, taking Delano Hill in the third round, Tedric Thompson in the fourth, and Mike Tyson in the sixth. It’s probably safe to assume that Schneider is already looking for Chancellor’s eventual replacement.

The questions don’t end with those two players. Thomas carries a cap hit of $10.4 million in both 2017 and 2018, and if he’s not the same player after a broken leg, what then? DeShawn Shead is already recovering from a torn ACL, and probably won’t be ready for Week 1 this year. No matter what happens in 2017, the Seahawks’ secondary is due for a makeover sooner rather than ever.

Russell Wilson’s health and supporting cast is crucial

With so much uncertainty on defense, 2017 might be defined by how much Wilson can carry the team. Bringing in Lacy and overhauling the offensive line is a start, but the Seahawks offense will go as far as Wilson can take them.

Wilson played through ankle and knee injuries last year and it clearly affected him: He had just 21 touchdown passes, down from 34 in 2015. He set a career high with 11 interceptions. His QB Rating was 92.6, a career low. And the lower-body injuries completely took away Wilson’s running threat — he managed just 259 rushing yards, by far the lowest of his five-year career.

This isn’t to say it was all bad news for Wilson. His receiving weapons were also done in by injury — Tyler Lockett’s broken leg was a huge loss late in the season — but Doug Baldwin had a career-best year with 94 catches and 1,128 yards. Jimmy Graham stayed healthy and became a bigger part of the offense, finishing with 65 catches for 923 yards. And Paul Richardson stepped up big in Lockett’s place, making huge plays down the stretch as Seattle solidified a playoff spot.

When Wilson is healthy and able to run, he adds a unique dimension to the offense that not many teams can match. And his weapons, aside from mistake-prone Jermaine Kearse, are reliable more often than not. However, the Seahawks must do a better job protecting him, and the running game needs to step up, as well. Wilson is a great quarterback, but he can’t do it all by himself.

The Seahawks’ transition period is coming

Pete Carroll and John Schneider built a perfect blueprint that set up Wilson for success: a punishing run game and shutdown defense. They rode that formula to two straight Super Bowl appearances, but have seen diminishing returns ever since then.

That core is not so young anymore, and while the team remains a contender in 2017, it’s time for the franchise to look at the big picture and start planning for the next generation. Bill Belichick didn’t build a dynasty by staying loyal to players and keeping them around past their expiration date, so Carroll and Schneider would be wise to learn from the team that beat them in Super Bowl 49.

The Seahawks will be good next season. They might even be great, depending on injury luck and how the new talent acclimates to the culture Carroll established. But after 2017? That’s when the hard decisions come up.

Carroll and Schneider have done an impressive job building a yearly contender, but they’ll be under pressure to handle those decisions correctly. The next couple years could ultimately define their legacy in the Pacific Northwest.