INDIANAPOLIS — Same sum, different math.

The Indianapolis Colts’ improbable run continued Sunday with a 27-23 victory against the Tennessee Titans at Lucas Oil Stadium.

The game hewed close to a familiar script on many themes. Indianapolis improved to 8-1 in games decided by one score or less, and it was the seventh straight home game to come down to the final drive.

But the Colts (9-4) tweaked the ending a bit this time around. It was the defense making the big, game-changing plays and the offense holding on to the lead late.

“It was a great team win again, and like I said earlier, there won’t be any blowouts with this team,” Indianapolis interim coach/offensive coordinator Bruce Arians said. “This team is too young. We just try to figure out a way to win every week, and so far we’ve been able to do that.”

The latest victory brings the Colts to the brink of the postseason. Losses by the Pittsburgh Steelers (7-6) and Cincinnati Bengals (7-6) on Sunday gave Indianapolis a two-game lead for the AFC’s fifth playoff spot with three regular-season games to play.

The formula for the Colts clinching a playoff spot remains convoluted, taking into account possibilities such as the 6-7 New York Jets winning out and the Bengals and Steelers playing to a tie in their Dec. 23 meeting.

Indianapolis also will remain alive in the race for the AFC South title if the 11-1 Houston Texans lose tonight against the 9-3 New England Patriots.

With so much uncertainty remaining in the picture, it’s best the Colts remain focused on tending to their own business.

Against Tennessee (4-9) that meant overcoming a rugged first half that left Indianapolis with a 20-7 deficit.

Andrew Luck was responsible for part of that margin, throwing his third interception that was returned for a touchdown late in the second quarter with the Colts trailing 10-7.

Replays appeared to show at least one of Luck’s knees — if not both — was down before he released the football. But referee Peter Morelli didn’t see enough on video to overturn the call.

“I saw it on the [video board],” Luck said. “I was hoping that they would call me down. But I probably deserved a pick-six for trying to throw a football in that position going down, right at a defender. So learn from it, and don’t do it again, hopefully.”

The Titans also scored on an 18-yard pass from Jake Locker to Jared Cook on the game’s opening drive and a pair of Rob Bironas field goals in the second quarter.

Locker finished with 262 yards, but he gained just 49 in the second half and was intercepted twice.

“We were ahead of the chains in the first half and we weren’t in the second, and that can make a difference,” Locker said.

Meanwhile, the Colts’ offense sprung to life.

After managing just a 4-yard touchdown pass to Reggie Wayne in the first half, Luck directed an 80-yard drive to start the third quarter that ended with a 1-yard touchdown run by Delone Carter and cut the deficit to six.

Cornerback Cassius Vaughn erased it entirely exactly three minutes later. On the first play after Pat McAfee pinned the Titans at their own 1-yard line with a 52-yard punt, Vaughn intercepted Locker’s pass and returned it 3 yards to the end zone for a go-ahead score.

Vaughn said Locker had been going to his side on intermediate routes throughout the first half. He gambled the quarterback would try the same thing again and won.

“It was one of them moments where we knew we had to try to make a play,” he said. “We made a play, and that turned the game around for us.”

After the teams traded field goals, Darius Butler grabbed the second interception against Locker. His came at the Titans’ 28-yard line and set up a 40-yard Vinatieri field goal to end the scoring.

Tennessee had one final chance to win. The Titans picked up a first down at their own 30 but believed they had a third-and-short and called a quarterback sneak. Locker was stopped for no gain on the play and then threw a pair of incompletions to force a punt.

Indianapolis took over at its own 10-yard line. Vick Ballard picked up a first down with a 13-yard run, and Luck sealed the game with an 11-yard pass to tight end Dwayne Allen on second-and-10 from the 24.

Luck finished just 16-of-34 for 196 yards with one touchdown and two interceptions. But he surpassed Peyton Manning’s franchise record for rookie passing yards, and he’s now just 259 yards shy of Cam Newton’s NFL record.

As usual, however, the only record Luck was focused on was 9-4.

“I think it’s the best team game in the world, I really do,” he said. “You have to rely on so many guys and so many different phases of the game. It’s fun when you can get team victories.”