Darius Leonard called this game a must-win. He isn't wrong.
The easiest way for a team to make the playoffs is to win its division. The Colts are playing catch-up after a slow start and have already lost to the Titans this season. Losing both of the games in the season series, and slipping another game back in the division, will make winning the AFC South nearly impossible.
Similarly, winning a wild card berth is a crapshoot. It requires lots of wins down the stretch and key losses from other teams. A loss today will all but guarantee that the Colts will exit their Week 14 bye with a losing record.