PITTSBURGH -- For the second game in a row, a Pittsburgh Steeler suffered a knee injury that will force him to miss time.

Inside linebacker Robert Spillane suffered an apparent left knee injury in the third quarter of Monday's loss to the Washington Football Team and is expected to miss time, a source told ESPN's Jeremy Fowler.

Spillane will not need surgery and is expected to return this season, the source told Fowler.

Spillane's injury comes a week after starting outside linebacker Bud Dupree tore his ACL against the Ravens and was placed on injured reserve. Rookie Alex Highsmith played in his place Monday, recording 60 defensive snaps.

Spillane, who has one interception and two sacks this season, was already playing in place of starting inside linebacker Devin Bush, who tore his ACL against the Browns in Week 6.

Pittburgh's linebacking corps was thinned even further when fellow backup Ulysees Gilbert III went on IR with a back injury last month.

"We know our mentality somebody gets hurt its next man up," cornerback Mike Hilton said. "It's been like that since Devin went down early in the season and guys have stepped up. We're not frustrated or anything, we just know we must play better."

In an uncharacteristic move for the franchise, the Steelers traded for inside linebacker Avery Williamson just before last month's deadline to give the position a little more depth. That move is even more important with Spillane's injury, as Williamson played the bulk of Spillane's snaps in the second half Monday.