DALLAS -- Baker Mayfield, believed to be the first walk-on true freshman quarterback to start a season opener for a BCS school, threw for 413 yards and four touchdowns while running for another score as Texas Tech beat SMU 41-23 on Friday night.

It was quite a debut for the 18-year-old Mayfield and new Texas Tech coach Kliff Kingsbury, the former Red Raiders quarterback and at 34 the youngest coach at a BCS school.

Mayfield, who completed 43 of 60 passes, had an 11-yard TD run in the fourth quarter before throwing two touchdowns in the final 6 minutes -- 3 yards to Jakeem Grant and 22 yards to Reginals Davis.

Texas Tech has won 15 games in a row against its former Southwest Conference rival.

Eric Ward had 13 catches for 150 yards for the Red Raiders.