ALAMEDA, Calif. -- The Raiders don't have much to play for, having long ago been eliminated from playoff contention. For linebacker Ray-Ray Armstrong, however, the final two games of the season qualify as a golden opportunity.

With Sio Moore on season-ending injured reserve with a hip injury, Armstrong is getting a mini-audition on defense after playing almost strictly on special teams since being claimed off waivers from St. Louis on Oct. 6.

A safety in college who went undrafted out of Miami, Armstrong started in place of Moore at weakside linebacker during last week's 31-13 loss to the Kansas City Chiefs. Armstrong made a few flash plays in the game and finished with four tackles.

The 23-year-old is expected to start again this week when the Raiders close out their home schedule Sunday against the Buffalo Bills.

"It's always good to get game reps," Armstrong said. "I'm going out there just trying to take every game in and get better off of each mistake. You can't get the same speed of a game in practice. It's a lot different."

Moore, Oakland's colorful and outspoken linebacker, was among the team's leading tacklers before getting sidelined by a hip injury he's been nursing for nearly a month. He was placed on the injured reserve list on Tuesday.

That leaves first-round pick Khalil Mack as the Raiders' lone remaining starting linebacker still playing. Middle linebacker Nick Roach, who played every defensive snap in 2013, has been out since suffering a concussion in the preseason.

With Armstrong joining Mack and Miles Burris -- Roach's replacement -- on Oakland's first-team defense, the team has very little depth at linebacker. Undrafted rookie Bojay Filimoeatu is the only other linebacker on the 53-man roster.

Spencer Hadley, a practice squad player who was converted to fullback earlier in the season, was moved back to linebacker for Wednesday's practice to add some depth.

Interim Raiders coach Tony Sparano said he was encouraged by Armstrong's debut against the Chiefs.

"I thought Ray-Ray played well in the game the other day," Sparano said. "I felt him quite a bit, felt him in some pressures. I thought he did some really good things in the run game, got around the football quite a bit. He was active and played with a good edge to him.

"Ray-Ray's a young player, and I'm sure at some point you could get that young guy on a mistake that jumps up out of there, but that didn't happen this past weekend. This guy wasn't a linebacker prior to a few years ago, so all of a sudden he's playing linebacker and starting out there and doing those type of things. His skillset is more of a sub type of a player, but I liked what he did out there. He kind of had a little bit of slink to him and found the football."

Armstrong was a bit more subdued in his self-evaluation.

"I think it went OK but the end result is you want to win, so it doesn't matter how I played," Armstrong said. "Getting that win is what we're all going out to do. You're a backup so you have to expect those things, that at any point in time you can get out there. With limited reps in practice you still have to perform and do your job."