The Miami Heat and head coach Erik Spoelstra reportedly agreed to a four-year contract extension Saturday, per Ira Winderman of the South Florida Sun Sentinel.

According to ESPN's Adrian Wojnarowski, Spoelstra "quietly" negotiated the extension ahead of what would have been the final year on his deal.

The 48-year-old is set to enter his 12th season as head coach of the Heat. He owns a career regular-season record of 523-363 (.590) with eight playoff appearances, four trips to the NBA Finals and two championships.

Spoelstra is the second-longest-tenured head coach in the NBA behind only Gregg Popovich, who is set to enter his 24th year in charge of the San Antonio Spurs.

Although much of Miami's success from 2010-2014 is credited to the Big Three of LeBron James, Dwyane Wade and Chris Bosh, Spoelstra proved his worth as an NBA head coach during that stretch by effectively managing three of the game's biggest stars.

Spoelstra also seemed to earn the respect of Heat President Pat Riley, who is one of the greatest coaches of all time in his own right.

The Heat missed the playoffs last season and went 39-43, which marked only the second time they have finished with a losing record during Spoelstra's tenure.

Miami has missed the playoffs in two of the past three seasons and three of the past five, but there is optimism surrounding the team after a big offseason.

The Heat acquired four-time All-Star Jimmy Butler in a sign-and-trade with the Philadelphia 76ers to be their go-to guy. He will join a core that includes guard Goran Dragic, small forward Justise Winslow and center Bam Adebayo.

While the Eastern Conference is top-heavy with the likes of the Milwaukee Bucks and Sixers leading the way, the door is open for a team such as the Heat to contend for a playoff spot and a potential top-four seed.