Editor’s note: Fifth of an eight-part series breaking down the Broncos’ roster as they reboot under new coach Vance Joseph. Saturday: Defensive line. Up next: Linebackers.

The Broncos’ defensive rankings are weird to see in succession. Total defense: fourth. Scoring defense: fourth. Passing defense: first. Sacks: third. Turnovers: seventh. Defensive touchdowns: third. Rushing defense: 28th.

Rushing defense is what prevented the Broncos’ defense from being as good as it was in 2015 when it ranked third. The struggles started early in the season and never stopped.

The issues came at every level — defensive line, linebackers and secondary. It was a combination of poor tackling, inability to get off blocks and sometimes lack of talent. The primary responsibility for a defensive lineman in a 3-4 scheme is to stop the run, so we’ll focus on that position now.

The Broncos have one building block on the defensive line in Derek Wolfe. They essentially chose to re-sign Wolfe at a cheaper figure over backing up the Brink’s truck for Malik Jackson, who left for Jacksonville in free agency last year.

Wolfe played well enough to be selected as a Pro Bowl alternate, but his season was defined by injuries. He fought through a summer ankle injury, a fractured elbow and multiple neck injuries all season. He missed only two games, but he was affected by them.

Wolfe, who turns 27 in February, is entering the prime of his career. If injuries don’t stop him, Wolfe can be a key figure on the Broncos’ defensive line for at least the next few years. He’s the Broncos’ best run stopper and best pass rusher on the defensive line.

Other than Wolfe, there’s not much to get excited about on the defensive line. Denver’s 2016 second-round pick Adam Gotsis is the closest to being a building block for the future, but he had a disappointing rookie season. The Broncos hope Gotsis can make a big jump in year two.

Other than Gotsis and Wolfe, the Broncos have only two other defensive lineman from their 53-man roster under contract for 2017: Jared Crick and Kyle Peko.

Crick was a starter, but he had an average year. His cheap contract makes it likely he’ll return, but he’s best suited to be a rotational player if the Broncos can upgrade. Peko spent most of the season on the practice squad before being called up for the season finale.

The Broncos missed Jackson’s production opposite Wolfe, but they made the right decision by not meeting his contract demands. Still, they failed to replace him. That is a priority this offseason. Related Articles January 17, 2017 Building Broncos: QBs, Searching for the special one to lead Denver to greatness

January 18, 2017 Building Broncos: RBs, It’s still about C.J. Anderson’s health, production

January 25, 2017 Demaryius Thomas, Emmanuel Sanders are great, but Broncos need more weapons

January 26, 2017 Building Broncos: OL, Fixing the mess is a must, but it won’t be easy

January 25, 2017 Broncos Mailbag: If Trevor Siemian won, why another QB competition?

Signing Arizona Cardinals defensive end and Denver native Calais Campbell would be a huge splash, providing a great complement to Wolfe. Campbell likely will demand a contract similar to or better than the three-year, $31.5 million extension Seattle Seahawks‘ defensive end Michael Bennett signed in December.

The Giants’ Jason Pierre-Paul could be another high-profile option, but re-signing Vance Walker might be a more cost-effective measure.

The rookie defensive line class doesn’t appear quite as good as last season, but there’s still plenty of talent. Stanford’s Solomon Thomas, Michigan State’s Malik McDowell, Florida State’s DeMarcus Walker, Michigan’s Taco Charlton and Chris Wormley are among the top defensive ends, potentially available when the Broncos pick in the first two rounds.

The Broncos have needs at defensive end, but they will also need a nose tackle if Sylvester Williams isn’t re-signed. Williams was unhappy when the Broncos declined to pick up his fifth-year option last offseason and he may move on in free agency.

Philadelphia’s Bennie Logan, Kansas City’s Dontari Poe, Washington’s Chris Baker would all be an improvement over Williams at nose tackle, if the price is right. Florida’s Caleb Brantley, Clemson’s Carlos Watkins and Washington’s Elijah Qualls could be possibilities in the first three rounds.

It’ll be a meat and potatoes offseason for the Broncos as they try to find solutions on the offensive and defensive lines.