The NBA world entered the season believing the Golden State Warriors were unbeatable.

The Houston Rockets have used a reliance on 3-pointers, incredible isolation plays, and a versatile defense to build the league's best record and change the narrative.

The Rockets may be built to take on the Warriors, and many think a Rockets-Warriors playoff series would feel like the NBA Finals.

In September, the ESPN analyst and former NBA head coach Jeff Van Gundy expressed what many people were thinking heading into the season.

"The Warriors are going to win forever if everything stays the same," Van Gundy told Sirius XM radio.

He added that "we're going to play it out, and the Warriors are going to win," declaring the season "over."

Seven months later, a strange sort of new optimism is starting to boil around the NBA — maybe this season isn't over, thanks to the 57-14 Houston Rockets. The Rockets sit in first place in the Western Conference and own the best record in the league.

"I'm glad there's somebody," the NBA TV analyst and former NBA star Steve Smith said of a challenger to the Warriors.

"You have a debate that they can maybe beat them. And I'm not saying years before there was nobody … but I think right now people are saying, 'Oh, this Rockets team' ... Which I think makes it, competition makes it great for any league."

These Rockets look different

Mike D'Antoni has revamped his style this year with the Rockets. Ralph Freso/AP The Rockets have been arguably the most dominant team in the NBA this season. They own 14- and 17-game win streaks. They're 31-5 with the league's best offense and eighth-best defense since January 1.

A portion of the credit goes to head coach Mike D'Antoni, who has adapted his system in surprising ways. The Rockets are not a run-and-gun team like D'Antoni's past teams (14th in pace), and they're not the type of pass-happy team (24th in assists a game and 29th in total passes made a game) that his Phoenix Suns squads were.

Instead, the two qualities that perhaps best define the Rockets are 3-pointers and isolation plays.

The Rockets take 42 3-pointers a game, seven more than the second-place Brooklyn Nets. Through 71 games, they have attempted more threes than they have two-point field goals.

"It's a really unique twist on what Mike had been doing," said David Griffin, the former Cleveland Cavaliers general manager who is now an NBA TV analyst. "I think the marriage of Mike D'Antoni and Daryl Morey," the Rockets' general manager, "is among the best in the NBA because Mike is smart enough to understand the concepts behinds Daryl's desired system. You can tell the analytics have revealed some things to them."

The Rockets are always in search of threes, even early in the shot clock and without ball movement.

They do run a staple of D'Antoni's offensive philosophy: Push the ball ahead and swing it to an open shot. Sometimes those open shots are 3-pointers, even when they have open driving lanes.

Iso, iso, baby...?

In the past, NBA analysts have thought that reliance on 3-pointers can hurt a team in the playoffs. What happens when the team goes cold from the outside? Will the well dry up?

But this year's Houston squad is different, mainly because of the isolation skills of James Harden and Chris Paul. Both players have used their one-on-one ability to get a step on defenders, attract help, and then find open shooters.

Griffin said one-on-one ability had changed how people should view the Rockets' reliance on threes.

Relying on threes, he said, "could be a real concern if you had a system that was predicated on pace and space." He continued: "That's not what their system is predicated on. So when the game slows down in the playoffs and people are able to hold and grab more because the officiating is so different, they've got two guys that can go get shots. And it's not just a function of the threes they're taking — it's the type of threes they're taking."

The Rockets lead the league in isolation plays, and Harden and Paul lead all players in isolation plays, according to NBA.com/Stats.

Harden, the favorite for MVP this season, may be as close to unstoppable as there is in the NBA right now. His stop-and-go hesitation dribbles allow him to get by nearly any defender and get to the basket. Because teams fear the Rockets' shooting so much, they often switch any pick to keep players from getting open beyond the arc. Once Harden gets a mismatch he likes, he roasts the defender.

There's still some hesitancy from the NBA world to believe that this style of play can work in the playoffs.

"I've never seen a team run that much isolation and win a championship," TNT's Kenny Smith said, adding: "I've never seen that. I'm not saying it can't be done — I'll be interested to see it."

Even Griffin expressed doubt that in the playoffs, where defenders can play a little more physically, Harden and Paul could get to where they wanted as easily or draw fouls to go to the free-throw line.

Defense is key

The difference this year, to the TV analyst Steve Smith, is that the Rockets defend. Historically, D'Antoni's teams have not been known for their defense (though their defensive deficiencies are occasionally overstated). The Rockets finished 18th in defensive rating last season. This year they're 10th for the season, eighth since January 1, and third since January 27, when they began a stretch of winning 23 of their past 24 games.

Luc Mbah a Moute has been a crucial player for the Rockets. Eric Christian Smith/AP Having Paul up top has helped the Rockets on the defensive end, and Harden, once a punch line when opponents have the ball, has improved. But two keys to Houston's defense have been two under-the-radar signings during the offseason: Luc Mbah a Moute and P.J. Tucker.

With Mbah a Moute on the court, the Rockets have allowed 100.4 points per 100 possessions, which would be the best figure in the league if sustained. With Tucker on the court, they have allowed 103.9 points per 100 possessions, which would rank seventh.

D'Antoni occasionally goes to ultra-small lineups, with the 6-foot-6 Tucker or the 6-foot-8 Mbah a Moute at center. Not only do these lineups allow Houston to spread the court with five shooters, making Harden's and Paul's driving lanes more accessible, but it will also enable them to switch every position on defense.

One such lineup — Harden, Eric Gordon, Trevor Ariza, Tucker, and Mbah a Moute — has blitzed opponents by 41 points per 100 possessions, posting an outrageous 142.4 offensive rating. Another, featuring Paul in Ariza's place, has outscored opponents by over 30 points per 100 possessions.

The Rockets' size disadvantage in those situations doesn't scare them. In fact, they invite plays like the one below, where the rookie forward Zach Collins spends several seconds trying to post up Tucker before settling for a tough, low-percentage shot. These situations are where the Rockets' math-fueled philosophy plays out — they can outscore opponents if opponents want to run their offense like this.

In some ways, these lineups are ideal for facing the Warriors. The Rockets can spread the floor to keep up with the Warriors' explosive offense, and they can switch at every position, nixing some of the Warriors' advantages.

But Griffin, who knows a thing or two about matching up with the Warriors after three straight Finals matchups, notes one potential problem. Both Mbah a Moute and Tucker have been efficient from 3-point range this season, but neither, historically, is a great shooter. Opposing defenses will most likely lay off of them in the playoffs to clog the driving lanes for Paul and Harden.

Additionally, Griffin said the Cavs never wanted to let Stephen Curry rest on defense. The Warriors will often hide Curry on opponents' worst offensive threat; in the Rockets' case, that would most likely mean Tucker or Mbah a Moute. The Cavs tried to put Curry through the wringer on defense, screening him and forcing him to switch onto LeBron James or Kyrie Irving. The Rockets would most likely try to do the same with Paul or Harden to force Curry to spend as much energy as possible on defense.

Griffin also noted a logistical advantage the Warriors could have. If they're fully healthy, they may face the Rockets earlier than the Cavs ever did. In fact, the year the Cavs beat the Warriors in the Finals, the Warriors had just been through a grueling seven-game series against the Oklahoma City Thunder, and Curry was already battling a knee injury.

Still, even the NBA world is crossing its fingers to see these two heavyweights square off in the playoffs.

"That's gonna be a hell of a series when they play," the TV analyst Charles Barkley said.

"If Golden State is healthy, I would say that I would favor Golden State pretty heavily," Griffin said. "But I think Houston has the best chance that anyone in the West has had in quite some time."

Griffin added: "The closer to a Swiss Army Knife your roster can be, the better. And Daryl knows that, and he's built a team that's pretty versatile and interchangeable, and that's significant."

Even Van Gundy seems to have come around.

"I've been saying for the past month they're the second-best team by far to Golden State, and now I'm willing to say they're as good as Golden State right now," Van Gundy told Fox 26's Mark Berman before a March game.

"I think that Western Conference Final between Houston and Golden State is really the championship."