Oklahoma quarterback Spencer Rattler came into the season as the odds-on Heisman Trophy favorite.However, after freshman Caleb Williams replaced a struggling Rattler against Texas last week, Rattler’s job is in jeopardy.Sooners coach Lincoln Riley said he wouldn’t make an announcement before the game who would start at quarterback when No. 4 Oklahoma hosts TCU on Saturday.”We’ll see how the week plays out and we’ll see where we are when we get to Saturday,” Riley said. “The guys have done well.”Williams gave the Sooners a shot in the arm against the Longhorns, coming on with Oklahoma trailing 35-17 and leading his team to a 55-48 win. Williams threw for 211 yards and two touchdowns and ran for 88 yards and another score in that game, his first extended look in crunch time this season.Williams’ running ability gives the Sooners offense a different look, but TCU coach Gary Patterson said not much was fundamentally different with Williams at QB as opposed to Rattler.”Coach Riley does a great job of — he’s gonna put you in mismatches anyway, so you’ve got to really prepare for all of it,” Patterson said. “But I think you’ve got to look at, obviously they were doing it with the quarterback run game so that becomes a bigger part of their offense. But you’ve got to prepare for Oklahoma, not just the quarterback. They’ve got good players everywhere.”The Sooners (6-0, 3-0 Big 12) have won four consecutive games and five of six by seven or fewer points to stay undefeated and in the thick of the College Football Playoff race.TCU (3-2, 1-1) is coming off a 52-31 win at Texas Tech after dropping consecutive games.Running back Zach Evans has been the driving force behind the Horned Frogs’ offense, rushing for 586 yards and five touchdowns so far.Against the Sooners last season in Oklahoma’s 33-14 win, Evans had just one carry for 10 yards but had five catches for 56 yards.