THOUSAND OAKS, Calif. -- The Los Angeles Rams' defense could appear drastically different going into next season as the unit undergoes arguably its biggest makeover since Sean McVay became coach three years ago.

Gone is veteran defensive coordinator Wade Phillips, who came to L.A. in 2017 with McVay. Newcomer Brandon Staley will take over and inherits a defense that ranked ninth in efficiency last season, but one that had momentary and -- in three instances -- complete game meltdowns.

Staley is expected to maintain the 3-4 scheme installed by Phillips, but he could be down four key contributors from the get-go.

Veteran defensive lineman Michael Brockers, outside linebacker Dante Fowler Jr. and inside linebacker Cory Littleton are scheduled to become unrestricted free agents next month.

And last week, veteran safety Eric Weddle announced his retirement after playing 13 seasons, earning six trips to the Pro Bowl and two All-Pro honors.

Here's a look at questions facing each defensive position group this offseason.

Safeties

Weddle's production was down in his final season, but the 13-year veteran provided leadership and was the defense's on-field signal-caller last season. He had 108 combined tackles but no interceptions and only four pass deflections in a career that saw him pick off 29 and bat down 99. It's uncertain who will take over his duties going forward.

Taylor Rapp is expected to slide into Weddle's starting role after he demonstrated steady improvement throughout his rookie season. Rapp had two interceptions and six pass breakups.

John Johnson III will return from a season-ending shoulder injury for the fourth and final season of his rookie contract. Johnson has ascended into a leadership position and is among the defense's top playmakers. In six games last season he had two interceptions.

Marqui Christian, a key rotational player in the secondary last season, is a pending unrestricted free agent.

Defensive line

The line will look much different than it has the past seven seasons, with the exception of mainstay Aaron Donald.

Donald missed on a third consecutive NFL Defensive Player of the Year honor last season, but still had 12.5 sacks and is considered among the league's best defenders.

In 2020, though, he will likely play without Brokers for the first time. A force against the run, Brockers -- who just wrapped a three-year, $33.3 million deal contract -- is expected to earn another large payday elsewhere. It's uncertain who will replace him.

Morgan Fox, a restricted free agent, maintained a role as a rotational player last season and had two sacks. Justin Lawler, a seventh-round pick from SMU in 2018, spent last season on injured reserve because of a foot injury. Sebastian Joseph-Day, Tanzel Smart and Greg Gaines are expected to maintain similar roles as last season at tackle.

Outside linebackers

Fowler blossomed into the player that the Rams hoped he would be when they acquired him at the trade deadline in 2018. Last season, the fifth-year pro had a career-best 11.5 sacks and forced two fumbles.

Now he is due a payday.

Fowler is a candidate for the franchise tag (expected to be more than $13.2 million next season for linebackers) if the two sides cannot agree to a long-term contract.

There also remains the possibility that Fowler signs a long-term deal elsewhere, although he has expressed a desire to remain with the Rams -- even on a short-term deal or for potentially less money.

If Fowler does not return, the Rams could turn to Samson Ebukam -- a starter in 2018, and Ogbo Okoronkwo, who showed glimpses of his playmaking ability in spot opportunities last season.

Ebukam had 4.5 sacks last season and Okoronkwo had 1.5.

Clay Matthews III is expected to return for 12th season and the second of his two-year, $9.3-million deal with the Rams. Matthews was sidelined for three games last season after he broke his jaw in Week 5, but finished with eight sacks -- his most since 2014.

Inside linebackers

The Rams could lack starting experience at inside linebacker if Littleton departs in free agency.

An undrafted free agent in 2016, Littleton climbed from special teams standout to defensive starter after two seasons.

After leading the Rams in tackles in consecutive seasons and intercepting five passes over that same span, Littleton has expressed a desire to sign for his value, meaning it's unlikely he'll return in 2020 given the Rams' lack of salary-cap space and the team's history of letting inside linebackers go.

Micah Kiser, Kenny Young and Travin Howard are among candidates to replace Littleton or earn the second starting spot. Kiser was projected to start alongside Littleton last season before he suffered a season-ending pectoral injury in a preseason game.

After a string of injuries last season, Troy Reeder was elevated to a starting spot and finished with 53 tackles. However, the former undrafted free agent is expected to return to the role of a backup role going forward.

Cornerbacks

The cornerbacks group underwent a significant in-season makeover last season when Aqib Talib was placed on injured reserve, then traded to the Miami Dolphins, and Marcus Peters was traded to the Baltimore Ravens.

Those moves were made to acquire Jalen Ramsey, who returns for the final season of his rookie contract.

However, it remains uncertain who will start opposite of Ramsey.

Troy Hill and Darious Williams are the options currently on the roster.

Hill showed promise in nine starts last season, intercepting two passes, before he underwent thumb surgery and missed the final two games. Williams also is a young player who coaches have expressed confidence in. He intercepted two passes in each of his two starts at the end of the season.

Standout slot cornerback Nickell Robey-Coleman returns for the final season of his three-year, $15.7 million contract, though he could become a salary-cap casualty because of Hill's ability to play both outside and in the slot.