Colts, Jaguars, Texans and Titans will be fighting for the supremacy of the AFC south. Last year in 2016 season the Texans won the divition with serious doubts in the offense leaded by Brock Osweiler. But it was the defense who led them there. The other teams  had a difficlt time alomng the season. For example the Colts lose Andrew Luck for some games and the OL had problems to protect him. The Jaxonville jaguars had problems in their offense too, Blake Bortles wasn´t able to led an intresting offense.
Finally from the Tenesee Titans, they showed a strong OL just below Dallas. They had a consistent Runnign game with DeMarco Murray and Marcus Mariota srate developing as a good QB.

But, this will be different

In my opinion, the battle for the divition will be between the Houston Texans and the Tenesee Titans.

Houston texans have a  great defense, that defense led them to the divitional matchup lost against the New England Patriots in a game where the but the defense and the special teams gave opportunities to the Texans. With a rookie leading the offense, the Texans may have opportunities to improve their record.

In the other hand the Tenesse Titans have also improved their offense , stablished a good Rushing game and in the 2017 strengthen the passing game with Corey Davis and Taywan Taylor in 1st and 3rd round.

The Colts have struggled without Andrew Luck and the defense recieved many points and yards per game. So what they did in the 2017 Draft was that they improve their Defensive backs.

Finally the jaguars have struggled in the training camp with an inopertant offense.