Here it is, folks, the second round of the playoffs to end all second rounds of NBA playoffs.

The Golden State Warriors' likely matchup with the Houston Rockets -- a rematch of last year's Western Conference Finals that is coming around sooner than it ought to have come -- will consume most of the oxygen in the room over the next few weeks. And it should. There's a ton at stake out West: Full validation of James Harden's greatness, an end to or a continuation of one of the greatest dynasties in modern American sport, and a potential bellwether for the future home of Kevin Durant.

But that's not the conference we're talking about here. Because it's the second round in the Eastern Conference -- with matchups between the Milwaukee Bucks and the Boston Celtics on one side of the bracket and the Toronto Raptors and the Philadelphia 76ers on the other -- that might end up determining more about the hierarchy and power dynamics for the next few years of the NBA than anything that happens between the Warriors and the Rockets.

These are the two Eastern Conference series we've wanted for months. The Bucks have been the best team in the league since the beginning of the season, with a Mike Budenholzer-revamped scheme that has helped optimize Giannis Antetokounmpo and turned the Bucks into a team with perhaps the highest ceiling in the NBA. The Celtics' season, however, has been one dramatic rollercoaster ride -- a group that has far underachieved its preseason expectations yet still is easy to imagine going to the NBA Finals.

The Raptors have spent the past six months tinkering with lineup constructions in a way that's always had the playoffs in mind; the goal has always been, with this lone guaranteed year of Kawhi Leonard, to flip the script on the Raptors' great-in-regular-season-but-flop-in-playoffs history. They look the part of a versatile, dangerous playoff team, with a defense that may have the highest ceiling of any team remaining in the playoffs (fifth in defensive rating during the regular season, but third since the All-Star break). It's as if the Raptors have paced themselves all season for this moment. Whereas the team they'll go against has flipped its roster twice since the first game of the season – once when the Sixers traded for Jimmy Butler in November, the second time when they traded for Tobias Harris in February. The Sixers may have the biggest variance of any team left in the playoffs: At their best, they are title-capable, but they don't have much margin for error.

These are two series with incredible storylines that should stand on their own as great displays of playoff basketball.

But they also could signal much bigger things for the future hierarchy of the NBA.

Example A: The Boston Celtics. It's been a drama-filled season with very public fractures out of their locker room. But it's entirely possible this Celtics team can flip that switch. Granted, it was against the Victor Oladipo-less Indiana Pacers – that's no offensive juggernaut – but the Celtics defense looked as good in the first round as it has all season, giving up only 95.8 points per 100 possessions. (And that was without an injured Marcus Smart.)

Let's say the Celtics make the Finals. One would think that would make it very hard for Kyrie Irving to leave for the New York Knicks or another free-agent destination. But a loss in the second round would make it easy to imagine Irving pulling the cord on his Celtics career. Then what for Danny Ainge? Do you still mortgage the entire team in pursuit of Anthony Davis when Davis has been so vehement about wanting to go to the Los Angeles Lakers in 2020? Or do you start an abbreviated rebuild around youngsters like Jayson Tatum, Jaylen Brown and Terry Rozier?

Look at the team the Celtics will face: The Bucks seem all-in on their current iteration. They signed Eric Bledsoe to a four-year extension in the middle of this season instead of letting him entering free agency. Khris Middleton will be an unrestricted free agent this offseason, and all signs point to him staying in Milwaukee. A Bucks trip to the Eastern Conference Finals or the NBA Finals with the Giannis/Bledsoe/Middleton core would all but ensure the Bucks will throw massive money at Middleton to see this thing out. But what if the Bucks get upset in this second round? And what if one of the culprits for their loss is a poor showing by Middleton? That could sour the Bucks on paying him the kind of money he feels he deserves – or Middleton himself could look for greener pastures if he feels that a second-round loss exposed this team as a great regular season team that isn't built for a Finals run.

The other Eastern Conference series has just as much intrigue for the NBA's future. The Sixers are a team with one of the highest ceilings in the NBA – that starting five is, when healthy, absolutely absurd – but they also have little margin for error, what with Joel Embiid's balky knee and a distressing lack of depth. If the Sixers make the Finals with this group, perhaps giving both Jimmy Butler and Tobias Harris max contracts would make sense. But get bounced in the second round and one or perhaps both could decide to bounce out of town. And who knows what a second-round exit could mean for Brett Brown?

As for the Raptors? They knew what they were getting into when they traded for Leonard: One year to prove to the Southern California guy that Toronto is a great place to live and the Raptors are a great franchise to play for. Maybe his decision is already set; there's been no shortage of tea leaves that have had him signing as a free agent this offseason with the Los Angeles Clippers. But how hard would it be for Kawhi to leave Toronto if this team gets past the Sixers, gets past either the Bucks or the Celtics, and, hell, why not, wins the whole damn thing? (I've thought since before this season started that the Raptors are the team with the best chance of upsetting the Warriors.) On the flip side, of course, the Raptors get bounced in the second round and it's fair to assume Kawhi is all but gone. Masai Ujiri could then fully remake the team in his image, an abbreviated rebuild around youngsters like Pascal Siakam, OG Anunoby and Fred VanVleet.

So here's what's at stake this round:

  • The Bucks could begin to establish themselves as the next great NBA team for a post-Warriors era, with a player in Giannis who could become the face of the league in a post-LeBron era.
  • The Celtics could either make their case for a 2019-20 roster that could include both Irving and Anthony Davis, or push Irving out the door with an early exit.
  • The Raptors could establish themselves as the perfect place for Kawhi to stay to win championships as a top-tier team in the East for the foreseeable future, or they could begin the process of an abbreviated rebuild.
  • The Sixers could make hay with this bizarre roster and make a case to keep this four-headed beast of Embiid, Ben Simmons, Butler and Harris. Or, if they lose in the second round, the future of Butler and Harris feels very much in doubt – not to mention head coach Brett Brown.

From a basketball perspective, the second round of the Eastern Conference playoffs will be fascinating. Both of these series will be great watches and high drama.

But the more intriguing thing about these series isn't what they mean for the 2019 playoffs. It's what they mean for the future of the NBA.