Baylor is 6-0 and ranked No. 18 in the country, but the Bears reportedly will be without their best defensive player for the rest of the season.
Fifth-year senior linebacker Clay Johnston suffered a knee injury in Saturday's double-overtime victory over Texas Tech, multiple outlets reported Sunday, citing a school official.
Johnston has 58 tackles, including eight for loss and 2.5 sacks, as well as an interception and five pass break-ups.
Johnston, who has 28 more tackles than any other Baylor player, has been the middle linebacker in its 3-3-5 scheme. The Bears are 17th nationally in scoring defense (17.8 points per game) and tied for 39th in total defense (340.2 yards per game).
Johnston earned second-team All-Big 12 honors last season, when he made 99 tackles.
Baylor has made a surprising run into the Top 25 this season, with league victories against Iowa State, at Kansas State and Texas Tech to tie Oklahoma atop the Big 12 standings. The Bears play Saturday at Oklahoma State, which has the nation's leading rusher, Chuba Hubbard, who is averaging 182.3 yards per game.