This is obviously not a huge blow for the Titans unless Chris Johnson goes down with an injury. It does mean that the Titans will have to make a roster move, which is something that they have not had to do for the last 9 weeks. That is pretty much unheard of in the NFL today.
Wyatt also tweeted earlier today that Matt Hasselbeck's calf injury doesn't appear to be a tear. It is likely that he will miss at least one game, but it is not something that is going to land him on IR. Wyatt compared it to the injury Kerry Collins had last season that forced him to miss 2 weeks.
It will be good for Locker to be able to take the reigns over the next couple of weeks. He can fight to keep this team in the playoff hunt and gain some valuable experience for next season.