The Titans have exercised the 2018 option on tight end Luke Stocker, according to Field Yates of ESPN.com (Twitter link). Per the terms of the option, he’ll receive a $125K bonus and can make up to $1.375MM more this season. 
The Bucs waived Stocker just after Thanksgiving and the Titans signed him once he cleared waivers. It was a two-year deal for Stocker, but it included an escape hatch for Tennessee. They have elected to keep him to see what he can do in camp this summer.
Stocker, 30 in July, appeared in three games for Tampa Bay and one game for Tennessee in 2017, totaling just four catches for 30 yards and one score. He has never caught more than 16 passes in a season, but he does offer above-average blocking skills.