Arch Manning is in concussion protocol and did not practice Monday after suffering a head injury Saturday, when Texas turned to backup quarterback Matthew Caldwell to survive an upset bid by Mississippi State in overtime.

The No. 20 Longhorns enter the week with an unclear picture at quarterback and No. 9 Vanderbilt headed to Austin, but Texas head coach Steve Sarkisian voiced confidence in the to-be-determined plan.

If Caldwell starts, the fifth-year senior who called an audible before taking the snap on the game-winning TD pass at Mississippi State, has already earned the trust of teammates.

"He's played well every time that we've put him in the game," Sarkisian said Monday. "What gives me confidence is who he's been, so I feel very comfortable with Matt whenever he's in the ballgame.

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