While Garrard is indicating he is ready and willing to go, he's been limited in practice this week. Gray has started in his place the last two weeks after he suffered a high ankle sprain against the Colts on Oct. 22.
Titans coach Jeff Fisher said his team isn't building a defensive game plan around either quarterback.
"Their offense is really not going to change," Fisher said. "If Garrard comes back, he's a little more mobile than Gray. But they're going to run the football, play-action pass and try to keep our offense off the field.
"From what we've heard, (Garrard) has not practiced full speed, and the high-ankle (sprain) can be ... difficult."
Jacksonville coach Jack Del Rio indicated there's a chance the Jaguars won't name a starter until Sunday.
The Titans have pummeled two second-stringers in recent weeks, sacking Oakland's Daunte Culpepper five times and Carolina's David Carr seven times in back-to-back wins.