Andrew Luck threw three touchdown passes as the Colts won Sunday night at Tennessee to reach the AFC playoffs. (Andy Lyons/Getty Images)

Every NFL season features unlikely success stories and improbable playoff teams. But few have been more improbable than this season’s Indianapolis Colts.

Last offseason, the Colts couldn’t hire a head coach, being snubbed by their top choice when Josh McDaniels backed out of a tentative deal. Their franchise quarterback, Andrew Luck, couldn’t throw a football, at least for public viewing, until June. When the Colts finally landed a coach and got Luck back on the field, they started the season with one victory in their first six games. The entire situation appeared rather calamitous.

By late Sunday night, it all looked so different. Luck is as good as ever, with the NFL’s comeback player of the year award virtually certain to be his. Frank Reich has done a coaching job as impressive as any in the league. And the Colts are the AFC’s No. 6 seed, reaching the playoffs as a wild card by virtue of their 33-17 triumph at Tennessee.

“It’s been a lot of fun,” Luck told NBC after the game. “It’s been a journey, that’s for sure. I think what this team is doing is enjoying the journey. It’s a great group of guys. I can say this with full sincerity: I love playing on this team.”

The Colts, winners of nine of their last 10 games, become the third team ever to reach the playoffs in a season in which they started 1-5, joining the 1970 Cincinnati Bengals and the 2015 Kansas City Chiefs. They’ll play the third-seeded Texans, with whom they split their two meetings during the regular season, on Saturday in Houston.

The Colts’ loss to the Texans came in Week 4 in Indianapolis, an overtime defeat in which Reich took an ill-fated fourth-down gamble instead of settling for a tie and handed Houston its winning field goal. If that loss had been a tie, the Colts would be the division champs and the hosts of next weekend’s game. But that was one of the few coaching missteps by Reich all season, and the aggressive mind-set he was trying to establish with that move perhaps played a part in the Colts turning around their season.

“To do what we just did is a pretty good feeling,” Reich said at his postgame news conference Sunday.

Reich and General Manager Chris Ballard deserve plenty of credit. Ballard didn’t get flustered when McDaniels, New England’s offensive coordinator, reneged on his agreement with the Colts after last season’s Super Bowl. Ballard regrouped and got the Super Bowl-winning offensive coordinator, grabbing Reich from the Philadelphia Eagles.

Ballard also reconstructed the Colts’ offensive line to prepare for the return of Luck, who missed all of last season when his recovery from shoulder surgery went awry. Luck threw three touchdown passes Sunday night to give him 39 for the season, second-most in the league to the 50 by the Chiefs’ Patrick Mahomes. He’s back, all the way back, and that’s a big reason for the Colts’ success. But another big reason is the progress made by an offensive line that can now be described as sturdy. That never could be said earlier in Luck’s NFL career.

“They’ve been great,” Luck said. “They are hard-working, tough guys. They’re fun. They’re mean. They’re nasty. I wouldn’t want to play behind anybody else.”

Luck made one terrible throw Sunday night, handing the Titans a touchdown on an ugly interception after the Colts had built a 14-0 lead. But the Titans couldn’t keep pace with Blaine Gabbert starting at quarterback in place of the injured Marcus Mariota. Gabbert threw two interceptions, including one in the fourth quarter that led to a Colts’ field goal and a 27-17 lead.

So now the Colts are in the playoffs and they’re actually a dangerous team in this postseason given how they’ve played lately. They won in Houston in early December, snapping the Texans’ nine-game winning streak.

“Certainly what happened previously doesn’t matter in a game,” Luck said. “Each game is its own cycle. We know it’s a great challenge …. We’ll prepare and see what we can do.”

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