Marcus Mariota came off the bench to complete 12 of 18 passes for 100 yards, and the visiting Tennessee Titans held on for a 9-6 win over the Jacksonville Jaguars on Sunday afternoon at TIAA Bank Field.Ryan Succop put Tennessee (2-1) on top for good when he drilled a go-ahead, 28-yard field goal with 4:06 remaining in the fourth quarter. Succop connected on three field goals for all of the Titans’ scoring.Josh Lambo made two field goals for Jacksonville (2-1), which was trying to open the season with three straight wins for the first time since 2004. Jaguars quarterback Blake Bortles finished 21 of 34 for 155 yards and was sacked three times.Blaine Gabbert started at quarterback for the Titans but left with a concussion in the first quarter. Jaguars defensive tackles Calais Campbell and Malik Jackson sandwiched Gabbert on third-and-19. Jackson drew a 15-yard penalty for lowering his helmet to initiate contact.Gabbert completed 1 of 3 pass attempts for 8 yards before he was replaced by Mariota, who did not start because of a lingering nerve issue that has affected his ability to grip the football.Titans cornerback and punt returner Adoree’ Jackson also made an early exit because of a concussion. Jackson was slammed on a punt return by Jaguars tight end James O’Shaughnessy, who led with his shoulder and immediately dropped Jackson to the ground.The score was even at 3 at the half.Succop drilled a 39-yarder to open the scoring for Tennessee with 4:59 to play in the first quarter. The kick followed a nine-play, 27-yard drive in which Mariota took over for Gabbert at the Jacksonville 29-yard line.