SEATTLE -- Washington senior linebacker Joe Mathis, who leads the team with five sacks, will miss Saturday's game against Oregon State due to an unspecified injury, a source with knowledge of the situation told Rivals prior to the game.

The Seattle Times first reported Saturday morning that Mathis would be out and was spotted wearing a boot on campus this week. Tevis Bartlett, another outside linebacker for UW, is out as well.

The timetable for Mathis to return is still undetermined, a source told Rivals. The source added that it's not anticipated that the senior BUCK will miss the remainder of the 2016 season, but did say it's not out of the question. UW is planning to reevaluate Mathis' health coming out of the weekend and make a decision after a second opinion.

Mathis, a former four-star defensive end from Upland, California, was once on the fence on deciding to transfer or remain at UW. But the hybrid pass rusher elected to stay and now is one of the true leaders on the Huskies' defense.

Washington comes into its matchup with Oregon State the No.16 team in the country in yards allowed per game, while ranking sixth in scoring defense with just 11 touchdowns. A lot of the success has come with Washington getting pressure with four down linemen and not having to blitz.

Junior linebacker Connor O'Brien will replace Mathis as the starting BUCK having already played in all six games for UW this season.