The Pacers’ 13-game losing streak is the 2nd longest in NBA history by a team coming off a Finals appearance — the NBA record is 17 straight losses
There have been 6 teams (including the Pacers) that had a losing streak of 10+ games in the season immediately following a Finals appearance. Two of those teams had multiple 10+ game losing streaks that season, so their are 8 total streaks.
The longest losing streak in the season immediately following a Finals appearance is 17 by the 1964-65 San Francisco Warriors. The Pacers 13-game streak is the 2nd longest.
Below are the 6 teams and streaks:
Source: us, Basketball Reference.