Second in a series

The Raiders seemed happy with the play of Malcolm Smith as their every-down linebacker in 2015, and he remains under contract for a second season.

But that doesn’t mean they won’t bring in players both to compete with Smith and augment the unit as a whole, even though linebackers are off the field and often play limited snaps when defensive backs enter in nickel and dime sub packages.

The Raiders got good play out of Neiron Ball before he was injured and then Ben Heeney, who has the kind of energy and sideline-to-sideline capability the coaching staff loves.

But with more than $74 million in cap space, the Raiders can splurge on a linebacker if they wish, and there are two possibilities looking to make a big score with whom the coaching staff has familiarity _ outside linebacker Bruce Irvin (Seattle) and inside linebacker Danny Trevethan (Denver).

Irvin would provide a second outside pass rushing threat to go along with Khalil Mack (he’ll be listed as an end for purposes of this series) and Trevethan is just 25 years old and contributed to a Super Bowl championship.

A look at some possibilities when free agency begins March 9, as well as returning players and their own free agents:

UNRESTRICTED FREE AGENTS

Linebackers

OLB Bruce Irvin, Seattle: Had 5.5 sacks last season and has started 37 games over the last three seasons for one of the NFL’s fastest and most aggressive defensive units. Broke in as a rookie in 2012 with Ken Norton Jr. as his linebackers coach.

ILB Danny Trevethan, Denver: Became a starter for the first time in 2013 with Jack Del Rio as his defensive coordinator. Has the kind of speed the Raiders covet on defense and coverage skills that at times were lacking. Looked like he belonged on a top-flight defense, not as if he was being carried by it.

OLB Tamba Hali, Kansas City: Yes, Hali is 32 and his sack total dipped to 12.5 over his last two seasons. But he graded out very well according to profootballfocus.com, and with reduced snaps and playing on the opposite side of Mack, he could get back into double figures.

ILB Derrick Johnson, Kansas City: Also getting up there in age at 33, but a very respected opponent who has given the Raiders an eyeful over the past few seasons.

ILB James Laurinaitis, Los Angeles: Laurinaitis was somewhat of a surprise cut because the Rams don’t consider him an every down player any more and that’s how he was being paid. His role in Oakland would be strictly as a run defender.

ILB Brandon Marshall, Denver: Not quite up to par with Trevethan, but also 25 years old and was also installed as a starter by Del Rio.

OLB Junior Gallette, Washington: Personal issues led to his exit from New Orleans and make him an unlikely target for a Raiders team that likes to avoid drama.

PLAYERS UNDER CONTRACT

Malcolm Smith: In his first year as an every-down linebacker, Smith led the Raiders in tackles, had four sacks, a forced fumble and had a knack for showing up for key plays in close games. Had some issues in pass defense.

Ben Heeney: Not blindingly fast, but quick enough to have all the range he needs and fearless when it comes to making plays. Not really a true inside or outside backer _ just a football player.

Curtis Lofton: Originally signed to be a regular player, but quickly gave way to Smith because of deficiencies defending the pass. Solid in goal line situations and against the run. With a 5.35 million salary and $5.5 million cap number, could be candidate for contract downsizing as Nate Allen was _ if not release.

Neiron Ball: Flashed in a big way on special teams and with skill as both a pass rusher and on pass defense, and then it was over after five weeks because of a knee injury. The concern? It’s the same knee Ball had microfracture surgery on at Florida.

John Lotulelei: Promoted from practice squad during the season but had no impact on the 53-man roster.

Colton Underwood: signed to a reserve/future contract for a look-see in the offseason program.

UNRESTRICTED FREE AGENTS

Lorenzo Alexander: Could be brought back in his role as a special teams regular and steady locker room leader.

Aldon Smith: Will miss at least nine games because of suspension. Smith and Raiders have professed they want this to work. We’ll see.

RESTRICTED FREE AGENTS

None

EXCLUSIVE RIGHTS FREE AGENTS

Korey Toomer: Saw action in 10 games as a special teams player with four tackles.