BOSTON -- The typical NBA after-the-buzzer protocol suggests that each team's head coach should stand in front of their respective bench, crane his neck while searching for his counterpart, then deliver a friendly wave or finger point before retreating to their locker room.

After the San Antonio Spurs defeated the Boston Celtics 95-87 on Sunday evening at TD Garden, Brad Stevens and Gregg Popovich bucked that trend and met at center court for handshakes and a brief chat before Popovich delivered a playful slap on Stevens' side and dismissed the session.

Brad Stevens gushed about Gregg Popovich and Spurs saying "Obviously great coaching, great players, great system, great way of playing, complete buy-in, and a willingness to sacrifice across the board." Mark L. Baer/USA TODAY Sports

There's an obvious and unusual bond between these two coaches. They connected over Indiana roots and a love of well-executed basketball, and yet that's seemingly where the similarities stop. The 66-year-old Popovich likes to play the role of curmudgeon who has no time for your silly questions, while the 39-year-old Stevens overwhelms you with patience and kindness.

And yet Popovich has gone out of his way to both help Stevens and smother him with praise at every opportunity.

"I really respect what he does. I'll still watch his Butler tape, trying to learn some stuff he did there, to be honest with you," Popovich said of Stevens after Sunday's game. "I really respect the hell out of him. He's a really fine young coach, great demeanor. His team executes really well, and they're just going to keep getting better. So I enjoy him."

Stevens often gushes about the Spurs, their continuity, and their overall brand of basketball. He doesn't want his Celtics to be a carbon copy -- no one can ever be -- but he doesn't mind using them as a road map.

"Obviously great coaching, great players, great system, great way of playing, complete buy-in, and a willingness to sacrifice across the board," Stevens said. "All of those things stand out and what makes them great is they've got all that. Take away any part of that and it wouldn't be as good as it is. It's obviously been special to watch from afar."

Added Stevens: "I think the most important thing is to become the best us. So to go and try to be somebody else or be exactly like somebody else, especially technically or tactically, might not be the right answer. But as far as how [the Spurs] operate, their unselfishness, their clear desire for team achievement and, obviously, as a coach you aspire to learn from the best and [Popovich has] certainly separated himself as that.”

Stevens has often talked about a desire for “corporate knowledge” and believes that, with a young core in place, the Celtics are finally building towards that goal. And every game against the Spurs offers a chance to gauge exactly where Boston stands in its own building process.

Sunday's tilt was a reminder of the strides Boston must make and the questions that must be answered. Can the Celtics develop a homegrown superstar like Kawhi Leonard, who cranked up his activity in the fourth quarter and made plays all over the floor? Will the Celtics eventually develop the sort of sustained contender that can attract a premiere free agent like Spurs summer import LaMarcus Aldridge, who put up 24 points and 14 rebounds and had a series of clutch buckets in the final frame.

The Celtics, losers of two of their first three games, have more pressing issues like paring down a rotation that went 11 deep the past two games but Stevens is still figuring out how to best mix-and-match a roster overflowing with evenness. He isn't worried about being the Spurs at the moment, he's worried about giving his team the best chance to beat Indiana on Wednesday night.

But the kind words and advice from Popovich will resonate. Many have wondered if Popovich, recently named the successor as head coach of USA Basketball after the 2016 Olympics in Rio, will consider Stevens for an assistant job.

For his part, Popovich dismissed those questions on Sunday while noting that he can't truly ponder it until Mike Krzyzewski hands down his clipboard. Stevens, who was thrilled to see Popovich land the gig, has stressed that he would leap at any opportunity to be part of that staff. A union seems inevitable.

After all, these two coaches can't seem to get enough of being around each other.