If you're a head coach in today's NBA, you shouldn't expect to keep your job for long.
Since the spring of 2013, 13 coaches have either resigned, been fired or didn't have their contracts renewed. That includes George Karl, the league's 2013 Coach of the Year, and Lionel Hollins, who helped lead the Memphis Grizzlies to a surprising berth in the 2013 Western Conference Finals.
"At the moment, your average NBA coach seems to have the career tenure of an NFL running back," writes NBA.com's Steve Aschburner. "Longevity has turned into short-evity."
Heading into 2013 training camp, nine teams have rookie head coaches: the Atlanta Hawks, Boston Celtics, Brooklyn Nets, Charlotte Bobcats, Denver Nuggets, Memphis Grizzlies, Philadelphia 76ers, Phoenix Suns and Sacramento Kings. Four others—the Cleveland Cavaliers, Detroit Pistons, Los Angeles Clippers and Milwaukee Bucks—have new head coaches leading the way, too.
All that upheaval in one six-month span leads to an ungodly amount of uncertainty among the NBA coaching ranks. Nearly half the league's head coaches are a complete and total mystery at the moment.
With those question marks in mind, I set out to sort through the league's best and worst coaches. These rankings are predominantly based on three factors: a coach's career win-loss record, his recent success with his team and whether he's exceeded or fallen short of expectations, based on expected win totals.
Note: Unless otherwise noted, all statistics, point-differential figures and win-loss records come from Basketball-Reference. Expected win totals from the 2012-13 were calculated based on this formula from Justin Kubatko.