The Titans clearly are taking a more conservative approach with the health of Locker, who has dislocated his left shoulder twice this season. Hasselbeck helped lead the Titans to a 26-23 win over the Pittsburgh Steelers on Thursday night.
Don't be surprised if this is the last start Hasselbeck makes. Munchak was optimistic last week that Locker would play against the Bills, so he must be close. Barring a setback, it's likely he'll be back in the lineup when the Titans host the Indianapolis Colts in Week 8.
Hasselbeck arguably is the best backup quarterback in the NFL in terms of experience and ability, though he has been a middle-of-the-road player this season. If the 2-4 Titans have a run in them, Hasselbeck will need to take advantage of a poor Bills defense.
Follow Dan Hanzus on Twitter @danhanzus.