The Titans are planning on having Jake Locker as their starting quarterback this season, but they didn’t exercise his 2015 option so there could be a change before next year. If there is, sixth-round pick Zach Mettenberger could be the man to step into the lineup. The Titans took care of an uncomplicated, but necessary, step toward keeping that door open by signing Mettenberger to his four-year rookie deal. Jim Wyatt of the Tennessean reported the deal, worth $2.22 million with a $125,116 signing bonus was done. Another, more complicated step is Mettenberger’s return from last year’s torn ACL. Mettenberger was able to throw at the team’s rookie minicamp over the weekend, but he wasn’t feeling 100 percent. “I am not moving as fluidly as I have in the past but I am working hard to get back there,” Mettenberger said, via the Tennessean. “Being in the brace for two months, trying to learn how to walk, you lose a lot of muscle. … I just have to keep working.” Mettenberger is the third of six Titans draft choices to sign with the team.