The Texans lost their first three games of the year, and the Colts hobbled to a 1-5 record to begin the 2018 campaign.
The teams, both coming off 4-12 records last season, battled back to set up Saturday's improbable opening playoff game.
Houston's (11-5) turning point came at the expense of the Colts in Week 4 when Texans kicker Ka'imi Fairbairn connected on a game-winning 37-yard field goal to give his team a 37-34 win.
The win over the Colts started a nine-game winning streak for the Texans. They didn't suffer a defeat until the Colts traveled to Houston and posted a series-tying 24-21 win on Dec. 9.
The Texans won two out of their next three to clinch the AFC South for the third time in four seasons, and became the sixth team since 1980 to make the postseason after a 0-3 start.
Indianapolis (10-6) shifted the course of its season following a 37-5 blowout victory against the Buffalo Bills on Oct. 21. The Colts suffered a 42-34 loss against the New York Jets the previous week, but used the dominating win over the Bills as a springboard and posted a 9-1 record the rest of the way.
The Colts clinched their first postseason berth since 2014 with a Week 17 win over the Tennessee Titans. Indianapolis joined the 1970 Cincinnati Bengals and 2015 Kansas City Chiefs as the only teams in NFL history to make the playoffs after a 1-5 start.
Houston is led by second-year quarterback Deshaun Watson, who will make his postseason debut this Saturday. He finished with 4,165 passing yards on 345-of-505 passing with 26 touchdowns and nine interceptions this season.
Watson is opposed by Colts veteran quarterback Andrew Luck, who will play in his first playoff game since the 2014 season when the Colts reached the AFC Championship Game.
The 29-year-old quarterback was slowed by an injury to his right throwing shoulder that forced him to miss the entire 2017 season. Luck returned this year and threw for 4,593 yards and ranked second in the NFL with 39 scoring passes.
"He's a fighter, he never gives up," Watson said about Luck. "The game is never over. He slings that thing. He throws it 60 times a game, you rarely see him frustrated. He just keeps fighting back, keeps battling, so the game is never over with him."
The Colts lead the all-time series by a 26-8 margin, and are 12-5 against the Texans at NRG Stadium. Indianapolis has won three of the last four meetings against Houston.