Real plus-minus rates Kristaps Porzingis No. 1 in rookie rankings

Kristaps Porzingis has built a strong early RPM with some solid defensive numbers. Tom Szczerbowski/USA TODAY Sports

NBA coaches have been saying it forever: Rookies hurt their teams on the court.

Last year, Jeremias Engelmann and I took a deep dive into the question, and we found the coaches are definitely on to something. First-year players rarely move the needle in a positive direction.

But things may prove a little different this year.

According to Real Plus-Minus (RPM), which estimates each player's impact on his team's net efficiency with mathematical modeling to adjust for the on-court effects of teammates and opponents, several rookies have already found ways to help their teams win this season.

On the other hand, most rooks have been negative contributors -- just as they usually are.

Let's look at which rookies have made a notable impact in the early going. Some of the findings may surprise you. (Spoiler alert: Jahlil Okafor currently sports the worst RPM in the league.)