As HBO's new documentary featuring Bill Belichick and Nick Saban opens, the Patriots coach politely asks director Kenny Rodgers and the rest of the NFL Films crew to leave Saban's office so the two long-time friends can catch up. The start of that conversation is arguably the most fascinating element of the 75-minute documentary called "Belichick & Saban: The Art of Coaching," which is set to air Dec. 10 at 9 p.m. on HBO.

As the people file out, narrator Liev Schreiber explains that a single-shot camera remained in the room and picked up on the two legends getting reacquainted. Saban congratulates Belichick on his sixth Super Bowl title before the Patriots coach lets us know how he felt about the reigning champs.

"We were good for one-third of the season," Belichick explained. "We were [expletive] for two-thirds of the year."

The exchange is brief and soon we embark on a journey that eventually explains how the two legends careers became linked. The crossover came in 1982 when Saban joined the staff at Navy, where Belichick's father, Steve, was a long-time coach. The two met over the summer when Belichick was back visiting his parents and found his father had taken a liking to Saban and was quite helpful in his early development.

The similarities between the two are striking, from their shared Croatian heritage to their lack of patience with the media and their penchant for accentuating the strengths and hiding the weaknesses of their players. When Belichick was named head coach of the Cleveland Browns in 1991, Saban was his first phone call. At the time the Alabama legend was in his first season as head coach at Toledo, but Belichick convinced him to be his defensive coordinator.

While much of the behind-the-scenes footage shown in Cleveland was used in a previous NFL Films documentary "Cleveland '95: A Football Life," there was a great scene showing the aftermath of the Browns dramatic goal line stand to seal a victory in Dallas late in the 1994 season. Belichick hugged Saban on the sideline as the two celebrated, showing plenty of emotion while congratulating his defensive coordinator for a job well done (in language that was a bit more colorful than that).

The viewer gets a peek of loads of practice footage for both, displaying the incredible attention to detail from each coach. But it's the interaction between the two that stands out. As they stand watching Alabama's Pro Day last spring, Belichick bluntly asks his friend who the best player is. After a brief pause, Saban informs him that tackle Jonah Williams, who went 11th overall to the Bengals, and the defensive linemen top the list. Defensive tackle Quinnen Williams went third overall to the Jets. When the two were back in Saban's office, he interestingly explained to Belichick how some NFL coaches don't bother to speak to him before selecting some of his players, which he says leads to some bad choices.