Knicks fans were hopeful that first-round draft pick Jerian Grant would emerge this season as a starting-caliber point guard—something the team needs desperately. Instead, he’s barely gotten on the court for a team that has already been eliminated from playoff contention.

Grant, the 19th overall pick last summer, is averaging just 15.3 minutes a game for a non-playoff team. That’s very unusual in the NBA and, most alarmingly, an indication that the player is unlikely to develop into much more. Since 1970, only five other...