In one of the most shocking developments in NFL history, 2012 first overall pick Andrew Luck has retired at the age of 29.

It's a stunning revelation given the Stanford standout was still in his prime. However, injuries took their toll on the young field general:

It's an unfortunate circumstance for the talented 29-year-old. This decision has major ramifications not only for the Colts, but for the entire AFC South.

Indianapolis Colts

With the quarterback reins officially going from Luck to Jacoby Brissett, the Colts' offense will have to transition, even though Brissett has been a starter in Indy already. In Brissett's lone season as the starter for the Colts in 2017, he completed 276 of his 469 passes for 3,098 yards and 13 touchdowns to seven interceptions. He also came away with 260 rushing yards and four rushing touchdowns.

It's a severe dip from the production Indianapolis became used to with Luck under center, but the team isn't the same as it was during Brissett's one season as a starter. The Colts' offensive line is significantly improved from leading the league in sacks given up in 2017 (56) to allowing the fewest in 2018 (18).

Not to mention the severe turnaround with the defense behind the likes of Darius Leonard and Malik Hooker.  Plus, with the development of third-year running back Marlon Mack, the offense should be a little more focused on the run. This is especially true with the versatility Brissett brings to the table.

The Colts should be able to contend still, but they're not the favorite after Luck's retirement thanks to the improvements to the rest of the AFC South.

Houston Texans

The Colts aren't the only team that felt a severe change in the team's production, as Lamar Miller tore his ACL in Saturday's preseason game. The running back depth behind Millers isn't the most reliable, with glorified pass-catching back Duke Johnson likely taking over Miller's duties.

This isn't the best news for quarterback Deshaun Watson. He's going into his third season without a rushing attack and with one of the worst offensive lines in the league. He's coming off a season in which he was sacked a league-leading 62 times and was under constant duress.

The defense should still be able to keep the Texans in the game with the intense pass rush and defensive backfield they have. But with the offensive line struggles and Miller's injury, it could be a tough season for Houston. They may not be able to capitalize on the Andrew Luck retirement.

Jacksonville Jaguars

The Jaguars' offense is experimental at this point. They're in the first year of a post-Blake Bortles world, and now they're putting their trust into Super Bowl LII MVP Nick Foles. There are also still questions regarding the rest of the offense.

The receiving corps leaves a lot to be desired with the likes of Marquise Lee and Dede Westbrook leading the way at that position group. Running back Leonard Fournette is in a make-or-break year after a significant drop-off in his production that led to him being called out by executive VP Tom Coughlin. Not to mention the offensive line was one of the worst as they were tied for the third-most sacks allowed (53).

However, the defense the Jaguars have is something that will keep them in games. They should be able to return to their 2017 form with the additions and newfound depth to their defensive squad.

However, Jacksonville can't win every game with only the defense to bail them out. They'll need the Nick Foles experiment to pay off for them, as well as seeing Fournette return to his 2017 form. If the Jaguars can't recapture that same play they had two years ago, then they're likely out of the playoff picture.

Tennessee Titans

The Titans have a real shot at taking over AFC South supremacy with the retirement of Andrew Luck. They have an exciting young nucleus with the caliber of players they have on their roster. Derrick Henry, Taylor Lewan, Corey Davis, Adam Humphries, Dion Lewis, Jurrell Casey, Harold Landry, Logan Ryan, Adoree Jackson, and Kevin Byard are all going to take the Titans to new heights.

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But the biggest question mark of them all is at the quarterback position. Marcus Mariota needs to take that next step and show he was worth the No. 2 overall pick back in 2015. He has been inconsistent in the past and hasn't shown that elite level of play just yet. Mariota has the athleticism to take over, but he hasn't truly flashed as a passer.

Tennessee has already brought in Ryan Tannehill as a backup in case Mariota is unable to meet the expectations placed upon him. However, if Mariota can meet the expectations placed in front of him, then expect the Titans to be the new leaders of the AFC South.

What to expect in an AFC South with no Andrew Luck

It's going to be an interesting transition for the Colts going from Andrew Luck to Jacoby Brissett. If Brissett can't elevate his game, it's unlikely he'll take the Colts very far.

The Texans have been dealt a bad hand after the Lamar Miller ACL news. With the lack of support around Deshaun Watson on the offensive line, it's going to be a rough one to watch out in Houston.

The Jaguars are the wild card in this division. Their defense and rushing attack need to return to what they were back in 2017. Plus, Nick Foles needs to play like the big-money quarterback he signed on to be for Jacksonville.

Finally, the Titans have the best chance of taking over in the division. They have the youth and talent on their side. All they need is for Marcus Mariota to take that next step as a franchise quarterback.