There has been a 50 percent drop in black head coaches in the NBA from three years ago, the lowest total in 16 years.

"That's not enough," said Paul Silas, who is now retired after three decades in the NBA coaching ranks. "There are more guys that understand how to coach basketball. And they should have a chance."

From 2001-2014, the NBA averaged 11 black head coaches per season. On opening night in 2012, half of the NBA's 30 head coaches were people of color, including an all-time 14 black coaches.

The number has been declining ever since.

"I think it bears watching, to see what happens," said Alvin Gentry. "Five years from now, where are we going to be, from a numbers standpoint?"

Mark Tatum, the NBA's deputy commissioner, dismissed the downturn as "cyclical."

Over the last 10 years, white head coaches have lasted 3.2 seasons, on average, while black coaches have lasted just 2.85 seasons, according to a study of coaching tenures by Bleacher Report.

Turnover has been especially heavy in the last two-and-a-half years, with 29 coaches hired since the end of the 2012-13 season. Just 11 of those hires were black.