It only took two seasons for Joe Mazzulla to prove that he has what it takes to be an NBA coach.

Mazzulla was thrust into the spotlight in September 2022 when the Boston Celtics named him interim coach after Ime Udoka was suspended by the team for the entire 2022-23 campaign for violations of organizational policies.

Just 21 months later, the Celtics, under a 35-year-old Mazzulla who had his interim tag removed in February 2023, were hoisting the Larry O’Brien Trophy to mark their 18th title in franchise history.

But these types of success stories are rare.

Plenty of coaches have waited well over two years to make their mark, and here are three who need to do so this season if they want to refine their reputation.

Doc Rivers, Milwaukee Bucks

When it comes to causing title contenders to fall short of expectations, no one does it better than Rivers.

Rivers has been coaching powerhouses since the 2013-14 season, when he saw his Los Angeles Clippers go 57-25 in the regular season just to lose in the Western Conference semifinals.

Since then, despite having talent like Paul George, Kawhi Leonard and Joel Embiid playing for him, Rivers has never been able to coach a team to the Finals. He took over at the helm in Milwaukee back in January, with the Bucks going just 17-19 this past season under his watch.

Milwaukee then got bounced in the first round of the playoffs.

Any team with Giannis Antetokounmpo and Damian Lillard should — at the very least — be one of the last four teams standing in the Eastern Conference. If Rivers can’t help the Bucks make a deep playoff run this time around, we may never see him coach again.

Steve Kerr, Golden State Warriors

The Splash Brothers are no more.

An aging Klay Thompson joined the Dallas Mavericks in June via a sign-and-trade deal, leaving star guard Stephen Curry as one of the last remaining pieces of Golden State’s dynasty that dominated from 2014-22.

Draymond Green is still around, too, of course — when he’s not facing a suspension for turning a game into a cage match.

However, this Warriors team is now a shell of what it once was. 

Kerr has seemingly been carried by Curry, Thompson and at one point, Kevin Durant, for the entirety of his coaching career. With the teams Golden State has had over the past decade, you could throw in a third-grader at coach and they’d probably do just fine.

Now Kerr finally has the chance to show that he does know what he’s doing, but if he fails, don’t expect the criticism to be light.

Tom Thibodeau, New York Knicks

Based on the way New York fans have been acting this offseason, you’d think the Knicks had already won a championship.

New York traded for Mikal Bridges in July, putting him alongside Jalen Brunson, OG Anunoby, Julius Randle and Mitchell Robinson to make up a daunting starting five. On top of that, Josh Hart and Donte DiVincenzo will be coming off the bench, making the Knicks a serious threat in the East.

But this team is going nowhere if Thibodeau burns his guys out by mid-March.

Thibodeau is notorious for excessively playing his starters, but with New York’s strong second unit, hopefully that changes this year. If it doesn’t, Thibodeau could find himself being deemed Public Enemy No. 1 in the Big Apple.