https://www.nba.com/article/2019/08/14/2019-20-nba-schedule-notebook

Over the last 20 (full) seasons, there has been a strong correlation between a team's record after 20 games and its record at the end of the season. Really, there's a pretty strong correlation between a team's record after just 10 games and how it finishes the season. The correlation grows with each game and the 20-game mark isn't a significant inflection point in that regard. It is 1/4 of the way through the season and a benchmark that many teams use to take measure of just what kind of team they are.

Like, if you haven't won at least seven of those first 20 games, you're most certainly not going to make the playoffs. Only four of the 106 teams that have won fewer than seven of their first 20 games over the last 20 (full) seasons have gone on to reach the postseason.

On the other end of the spectrum, 92 percent of the 215 teams that have won at least 12 of their first 20 games have gone on to make the playoffs. That translates to about one miss per year