The Tennessee defense has kept them in games. Mariota has a couple good games here and there but he would never be able to outduel Luck even they had him tonight.
But when you look at their schedules, outside of that win over the Patriots (interesting how both Vrabel and Patricia beat him this year) the Titans beat bad teams. Specifically after getting destroyed by the Colts and Texans, they beat the Jets, Jags, Giants and Redskins before tonight. The Colts have also had a cake schedule but I think their wins were more convincing. They look the part, but we will see how they fare in the playoffs.