The Ravens invested heavily in their defensive line going into last season, using the draft, free agency and a major trade to reconfigure a unit that had faltered against Tennessee Titans uber-runner Derrick Henry in the 2019 playoffs.

Injuries and positive tests for COVID-19 kept the “Monstars” trio of Calais Campbell, Brandon Williams and Derek Wolfe from playing together for a chunk of the regular season, but come playoff time they smothered Henry in a rematch with the Titans and held up their end of the bargain in a low-scoring loss to the Buffalo Bills.

A defense that ranked eighth against the run in the regular season surrendered just 83 yards on the ground in those two postseason games.

The Ravens liked what they saw enough

to keep the band together, re-signing Wolfe to a three-year deal and retaining Williams in lieu of cutting him to create salary-cap space. They’ll rely on the imposing veterans to stifle opponents at the point of attack again in 2021.

They’ll also look for second-year defensive tackle Justin Madubuike to take a step forward after his promising debut. A knee injury hampered Madubuike out of the gate last season, but he showed big-play potential as a run stuffer and interior pass rusher down the stretch. He’s projected to play more snaps this year as the Ravens try to set up their future.

The path ahead is less certain for fellow second-year defensive tackle Broderick Washington, who struggled in limited snaps last season and was charged with destruction of property after he was arrested in Northern Virginia last month.

With veteran nose tackle Justin Ellis also back as a reserve candidate, the Ravens probably won’t have a lot of snaps to offer a rookie defensive lineman. If they draft an interior defender, which they almost always do, they’ll have an eye on 2022 and beyond.

What do the Ravens need at defensive line?

Youth, simple as that.

Wolfe is 31, Williams is 32 and Campbell will be 35 when the Ravens line up in Week 1. Only Wolfe is signed past this season. As set as the Ravens appear up front, they need young potential starters to line up beside Madubuike. They’d like candidates to bring pass-rushing punch to a group that has lacked it in recent seasons.

It’s not clear such prospects are widely available in a 2021 draft class that’s much better stocked at other positions.

Sirius XM analyst and former Dallas Cowboys executive Gil Brandt called this “one of the weakest years that I can remember in a long time for interior defensive linemen and defensive tackles.”

ESPN draft analyst Mel Kiper Jr. included just one defensive lineman in his most recent two-round mock draft.

“There’s not a lot there,” Kiper said. “When you look at the Ravens, I think Madubuike they really like, and they think he can be an outstanding player. So I just think the other needs [are greater].”

When Ravens general manager Eric DeCosta previewed the draft Monday, he did not list defensive line among the deeper positions.

“We’ll always look at the defensive line as being very important, especially in our defense and our scheme. Stopping the run is always a priority for us,” DeCosta said. “We were very happy last year with the additions of the guys we brought in across the board — the veteran players we brought in [and] the younger players. … We have some players that have one-year deals or two-year deals, [and] we have some younger players.

“So we’ll just continue to assess the strength of the draft. Quite honestly, if the best guy available at the time is a defensive lineman, then we’ll pick him. And if he’s not, we’ll pick somebody else.”

With that in mind, here are a few names the Ravens could target:

Alabama’s Christian Barmore

Why he’d fit: Barmore is the only defensive lineman widely projected to go in the first round after he dominated late in his one season as a starter for the Crimson Tide. He created havoc (12 combined pressures, according to Pro Football Focus) in Alabama’s two College Football Playoff wins, and his 6-foot-5, 310-pound frame, complete with long, powerful arms, is ideal for the NFL.

“He finishes, he gets sacks, and that’s what you want in a defensive lineman now,” Kiper said. “With his size and his length, he’s not a stay-at-home type. He’ll get after the quarterback.”

We know the Ravens love Alabama players, and Barmore’s versatile skill set would fit their scheme and long-term needs.

Why he might not: The Ravens also love prospects with long track records of production, and Barmore is not that. He did not start as a redshirt freshman and came up empty in some games (against Georgia, Tennessee and Florida) as a redshirt sophomore. That inconsistency led skeptical analysts to dub him one of the top boom-or-bust prospects in this year’s draft. Other scouts have picked at him for failing to establish consistent leverage advantages against the run

It’s not clear Barmore will even make it to the Ravens at No. 27 overall. His physical package and big-game performances as an interior pass rusher could prompt some team to pull the trigger five or 10 slots earlier. If he is on the board when the Ravens pick, would they take him over similarly graded players at wide receiver or edge rusher? It’s not out of the question given DeCosta’s commitment to picking the best player available, but it’s likely other prospects would do more to help the Ravens contend in 2021.

Projection: Round 1

Washington’s Levi Onwuzurike

Why he’d fit: Onwuzurike bursts off the line with powerful hands and showed he could handle multiple blockers as a starting nose tackle at Washington. He projects as a three-technique defensive tackle with pass rushing potential in the NFL. Pro Football Focus listed Madubuike as his NFL most comparable.

He was an excellent student and admired figure in the Washington program, and his sculpted frame also speaks to his work ethic.

Why he might not: Though he added significant weight at Washington, he’s still small (290 pounds) for an NFL interior lineman. He played out of position at nose tackle for the Huskies and would not project as a long-term replacement for Williams.

Onwuzurike opted out of the 2020 season and missed Senior Bowl week because of an injury

“He’s more of a guy who drops into the second or third round, just because he didn’t have the year and things didn’t go great after the season,” Kiper said.

Projection: Round 2-3

Louisiana Tech’s Milton Williams

Why he’d fit: Williams came on strong at the end of the 2020 season and projects as another versatile defensive tackle with upside as a productive pass rusher.

“He can be a three-technique,” Kiper said. “He can play outside. He can play a variety of roles up front, and he gets after the quarterback. He’s disruptive.”

Williams added significant weight in college, and scouts believe his frame can accommodate more bulk when he gets into an NFL weight room. He gets off the line quickly and moves fluidly for a man his size.

Why he might not: He did not play like a big-time prospect until the second half of his third season at Louisiana Tech and struggled in a high-profile matchup with BYU’s offensive line. At 284 pounds, he’s probably not sturdy enough to thrive in the NFL interior, so the Ravens would have to trust his ability to bulk up. Scouts also say he has a lot of refining to do after he played against middling competition in Conference USA.

Projection: Round 3-4

North Carolina State’s Alim McNeill

Why he’d fit: At 320 pounds, he’s a powerhouse who exploded off the line and handled double teams in his second season as a starter for the Wolfpack. He lined up over center and was strong enough to collapse the pocket as a pass rusher.

The Ravens will need to replace Williams, the longtime heart of their run defense, eventually, and McNeill would bring similar tools to their mix.

Why he might not: McNeill is raw as an interior pass rusher and did not make many plays in the backfield in 2020. He’s not as versatile as other defensive line prospects projected to go in the same range.

Projection: Round 3

Honorable mention

Iowa’s Daviyon Nixon (Round 3-4):All-around defensive tackle with a mean streak who was Big Ten Defensive Player of the Year in his one year as a starter at Iowa. Despite his production, scouts questioned his play-to-play consistency, especially against better offensive lines.

Texas A&M’s Bobby Brown III (Round 4-5): Massive and massively inconsistent nose tackle who looked awesome taking on multiple blocks in his best college reps. He needs a lot of work, but he’s only 20.

BYU’s Khyiris Tonga (Round 5): He’s a hulk with powerful hands and surprising mobility for a nose tackle. Scouts criticized him for not exploiting his physical advantages more consistently in college, but he would be an intriguing developmental prospect.