The Titans picked Herndon up from Seattle last June and agreed to a three-year deal with the veteran as they tried to shore up their secondary. That came after the season-long suspension of cornerback Pacman Jones.
But Herndon, who played in 73 regular-season games with Denver and Seattle with 49 starts, wound up being an expensive insurance policy in Tennessee.
He played in only four games and had just two tackles as second-year cornerback Cortland Finnegan won the starting job left empty by Jones' suspension.
Hadnot, 26, is a four-year veteran who has started 55 of 63 games with the Miami Dolphins. The Titans are looking at experienced linemen after losing starting left guard Jacob Bell in free agency to St. Louis.