Nylon Calculus: How does missing a rookie season affect development?

Last week the Sacramento Kings announced that would-be rookie Harry Giles, their first-round No. 20 overall pick, would redshirt this year while rehabbing his knee. At this point Giles may end up being joined in a virtual redshirt by the first overall pick Markelle Fultz who has sat since the first four games of the season with a mysterious shoulder issue.

Given that one of the aphorisms we often hear is that players need to play to develop, this must be a lost season for Giles and perhaps Fultz, right? That need to develop on the court is one of the reasons often given for tanking teams going young, letting the young guys play and develop.

In fact, in statistical projections I have run in the past found that the number of minutes played in a player’s rookie campaign is associated with more improvement in the future, even controlling for their per 40 minute production. But, there’s no way to tell if playing more is causing the player to improve. It is possible some rookies are playing more because either the coaches are picking up on cues from practice that they have more potential, or that the organization is more invested in them overall. It is perhaps somewhat telling that the biggest predictor of rookie time on the floor is simply where they were picked in the draft.

But, of course, neither Giles or Fultz would be the first player to redshirt his rookie year. Hell, Fultz wouldn’t be the first, or the second or even third player to redshirt on the Sixers in this decade. Overall, I was able to find eight first rounders since 2002 who had an injur- related redshirt, or near redshirt, in what would have been their rookie year and went on to complete the next year. The near redshirt players included were on the court for sixteen or fewer games before suffering an injury.

The interesting thing about these injury redshirts is that it forms something of a natural experiment with the decision to log court time being taken out of the team’s hands. For the most part the players do stay around the team, coaches and training staff doing what work they can and getting acclimated to the NBA. So, we can then look at whether when the player returns the next season they’ve developed, flatlined or regressed.

To do that I compared each of the eight redshirts return year to my model projection for their original rookie year. In seven out of the eight cases the redshirt player met or beat beat their rookie projection, with a mean and median difference equivalent of just under a +1 in plus-minus in the box score measure I used to evaluate players. The players used in the study are shown in the chart below with their actual performance minus the original rookie projection. Ben Simmons is not shown, though I would note he is currently on pace to finish above his rookie projection as well.

I should note that the difference between the redshirts residual over-under projection was not statistically significant at the 95 percent level, with a P level of .12. Tested against their projected sophomore year the return year was still slightly better on average projection, though again not significant at the 95 percent level.

Next: Nylon Calculus: Can LeBron James break the NBA points record?

The evidence here is hardly an open and shut case. But it should probably weaken whatever prior we have about playing time as the key to rookie development. Surely at some point live action playing time has to be part of the equation, but luckily for Giles and perhaps Fultz there appears to be  more to the equation.