NFL: Andrew Luck retirement, Lamar Miller injury flip AFC South projections

And just like that, the AFC South is completely up for grabs.

In one shocking Saturday night, Indianapolis Colts star quarterback Andrew Luck decided to retire, sending shockwaves through the NFL. Later that evening, Houston Texans starting running back Lamar Miller was injured and suffered what is believed to be a torn ACL, ending his 2019 season before it really got started.

The Colts now turn to Jacoby Brissett, a third-round pick in the 2016 draft who took over for Indy's offense when Luck was mired by injury in the 2017 season. Brissett completed 58.8 percent of his passes for 3,098 yards, 13 touchdowns and seven interceptions. He also rushed for 260 yards and four touchdowns as the Colts went 4-12. While Brissett offers a clear drop from the perennial Pro Bowler Luck, he should be well-prepared to run the show. 

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We'll find out quickly when the Colts open the regular season Sept. 8 at the Los Angeles Chargers. 

Meanwhile, Miller suffered a gruesome leg injury against the Cowboys on Saturday. His likely replacement just joined the team.

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Duke Johnson was acquired earlier this month in a trade with the Cleveland Browns. Johnson, a third-round pick in 2015, averaged 5.0 yards per carry last season but on just 40 attempts. He's never been asked to carry a lead-back role in the NFL, though he is the all-time leading rusher for the Miami Hurricanes.  

SportsLine data engineer Stephen Oh, whose SportsLine Projection Model simulated the NFL season 10,000 times, says the Colts' chances of winning the AFC South plummet without Luck, while the Texans' chances rise dramatically following Saturday's happenings.

Indy had 59.3 percent chance of qualifying for the postseason prior to Luck's announcement. That number plummets to 17.3 percent. The Texans' playoff chances went from 34.8 percent to 52.0.