Gregg Popovich has spent the last 25 years as the head coach of the San Antonio Spurs. The franchise has reached the mountain top five times under the legendary coach with the last one coming in 2014.

In the last couple of seasons, whispers have popped up about when Popovich might call it a career with the Spurs. Per Jake Fischer of Bleacher Report, there's still plenty of mystery involved.

The fact that Spurs officials and rival team personnel persistently whisper about his eventual retirement, when it will arrive, and who will ultimately replace him, is noteworthy in itself.

“Over beers, we always talk,” one former Spurs staffer said. “But nobody knows.”

“Nobody necessarily even internally knows,” the executive said.

Popovich certainly has earned the right to stay as long as he pleases and there is no pressure whatsoever for him to step aside anytime soon. There has just been a growing belief that this season could wind up being the last for San Antonio's longtime head coach.

So who could takeover for Popovich and the Spurs when he hangs it up?

Will Hardy, the respected Spurs assistant who just joined Ime Udoka's staff in Boston, has been considered a favorite for the job in recent years. Hardy is a young understudy who learned at Popovich's right hand, similar to how Jon Scheyer rose to replace Mike Krzyzewski at Duke.

Other names like Manu Ginobili, Tim Duncan, Becky Hammon and Brett Brown have been linked as well. For now, the Spurs will focus on trying to carve their way into a playoff spot this season.