NASHVILLE, Tenn. — The Tennessee Titans have kicked their youth movement into high gear with rookie Zach Mettenberger starting at quarterback against the Houston Texans on Sunday.

Jake Locker has missed three of the past four games with injuries, and coach Ken Whisenhunt said Thursday that the decision to go with Mettenberger was made Tuesday. The coach said this is an opportunity to see what the sixth-round draft pick out of LSU can do with the Titans struggling at 2-5.

“No question he’s a talented, young player, and maybe it’ll give us a spark,” Whisenhunt said. “Offensively, we haven’t exactly been lighting it up, so that’s part of it in consideration.”

Whisenhunt waited to announce the change to make sure Locker — who has been sidelined with an injured thumb — is healthy enough to back up Mettenberger. The coach also was trying to buy a day to slow down the Texans’ preparation for the rookie. The shake-up dropped Charlie Whitehurst, who started three of the past four games with the Titans losing two of those, to third on the depth chart.

Mounting losses and injuries seemed to make the change inevitable.

The Titans had stuck with Locker, the eighth pick overall in 2011, since hiring Whisenhunt in January. But Locker has missed 17 of a possible 39 starts and finished only three games this season because of injuries.

Mettenberger will become the fourth rookie quarterback to start in the NFL this season, the third quarterback for Whisenhunt. The Titans already are starting left tackle Taylor Lewan, linebacker Avery Williamson and running back Bishop Sankey with Mettenberger the fourth of six draft picks to start this season.

The quarterback dropped to the sixth round after tearing his left ACL on Nov. 29 playing for LSU but led the NFL this preseason with 659 yards passing. The rookie shaved the beard he started growing during training camp after practice just before talking to reporters.

“By no means am I a Tom Brady or a Peyton Manning,” Mettenberger said as he leaned back against his locker. “This is going to be my first game, so really I just got to get the ball out of my hands quick, avoid turnovers and put the ball in the (hands of) guys who can make plays for us. Really that’s the biggest thing a young guy’s got to do.”