OAKLAND, Calif. — A roar erupted from the team staff in the Houston Rockets’ locker room as the buzzer sounded. Ecstatic Rockets players hooted and hollered as teammate Gerald Green slapped hands with them outside the locker room door after the crucial 95-92 road playoff win over the Golden State Warriors. Even smiling veterans Chris Paul and Eric Gordon spoke to one another exuberantly after the series-tying Game 4 triumph in the Western Conference finals.

About the only Rockets player who didn’t appear in a celebratory mood on Tuesday, however, was their poker-faced and focused star James Harden.

“He realizes that this is an unbelievable opportunity that we cannot let pass us,” one Rockets source told The Undefeated. “He knows it’s one game, regardless to a win or a loss. He’s totally locked into this series. He’s business like I’ve never seen before. It’s the maturation of James Harden.”

Paul is a future Hall of Famer and a nine-time NBA All-Star. Clint Capela is one of the NBA’s best young centers and will be a coveted free agent this offseason. Gordon is one of the league’s premier shooters and sixth men. Trevor Ariza won a title with the Los Angeles Lakers in 2009. But there is no question that the pressure of the Rockets’ franchise weighs heaviest on Harden, who has done everything but win a title.

The bearded one is expected to win his first NBA MVP award. The nine-year NBA veteran has been an All-Star six times, an all-NBA first-team selection three times and led the league in scoring this season. Compton, California’s own also has won Olympic and World Cup gold medals with USA Basketball, is in the midst of a four-year max extenion. The contract is a super maximum extension that will guarantee him $228 million through the 2022-23 season, league sources told ESPN.

Assuming Harden will be MVP, the only thing he is missing is the Larry O’Brien NBA Championship trophy. He did make it to the NBA Finals as a member of the Oklahoma City Thunder with Kevin Durant and Russell Westbrook in 2012, but LeBron James and the Miami Heat took that hardware in five games, with Harden the third fiddle at that time. But now, this is Harden’s team with an opportunity for him at age 28 to return to the Finals. He is now two wins away from that feat.

The good news for the Rockets is Harden realizes that he can’t do it by himself. And after being drilled by the Warriors by 41 points in Game 3, Harden and the Rockets overcame their toughest adversity of the season by earning the gritty, hard-fought win. Lose and Houston is down 3-1 with an extreme long shot of upsetting the reigning champs to win the West.

“We’ve been doing it all year long,” Harden said. “That’s the main reason we’re in this position we’re in today. That third game was just one loss. We all know what that is. We’ve got the mentality that we’re going to win Game 4.”

Rockets head coach Mike D’Antoni and defensive guru assistant coach Jeff Bzdelik preached the needed improvement on defense during practice on Monday, sources said. You can debate all day about which high-octane offense is more powerful between Golden State and Houston. But ultimately, the West will be won on defense. To succeed, the Rockets desperately need Harden to be a factor on the only weak part of his game: defense.

The Warriors shot 52.2 percent from the field and made 19 of 32 3-pointers during a 126-85 blowout victory in Game 3. Stephen Curry scored 26 of his 35 points in the second half while Durant added 25 points. If the Rockets were going to leave the Bay Area with a win, they had to change their defensive mentality in a hurry. So according to sources, the Rockets’ defensive game plan was to dramatically improve on transition defense, switch aggressively, guard on defense like the season depended on it (which it did) and rebound better on both ends of the floor. Houston also wanted to be more physical. Harden had to step up too.

The Rockets didn’t appear to be heeding that message as they were skunked 12-0 to start the game at Oracle Arena. Not totally focused, the Warriors didn’t take full advantage of the Rockets’ poor start and finished the first quarter up 28-19 after missing four shots in the paint and turning the ball over four times.

”We just kept playing …,” Paul said. “We knew over the course of the game that at some point we were going to score. So, when it did happen, we tried to get some stops. When they made their push in the third quarter, you just know at some point they’re going to do it. They’re capable of it, but we are too. So at the end of the day, we keep saying it game in and game out, it’s who does what they do better than the other team.”

Harden and Paul had 15 and 14 points, respectively, and combined for five 3-pointers in the second quarter to get the Rockets not only back in the game but in the lead too. Houston outscored Golden State 34-18 in the second quarter to take a 53-46 advantage.

The Warriors recovered to outscore the Rockets 34-17 in the third quarter to vault back ahead 80-70 after the home team’s four All-Stars — Durant, Curry, Draymond Green and Klay Thompson — each earned a plus-17 in the frame while playing the entire quarter and combining for 28 points. The Warriors, sans an injured Andre Iguodala, actually went up 82-70 on a Shaun Livingston dunk with 10:45 remaining in the game.

With Oracle roaring and the Warriors being the Warriors, word was that Harden refused to give up and wouldn’t allow his teammates to either, as he kept telling them they would win.

“He willed us to win tonight both offensively and defensively,” the Rockets source said. “He refused to let us lose tonight. His energy and leadership throughout the game was remarkable. He just kept telling the guys all night that we’re going to win this game, and they believed him.”

The Rockets responded, finishing the game with a 25-10 run en route to the mammoth victory. Seven Rockets players scored in the fourth quarter of a game where only those seven played. Harden struggled in the fourth quarter offensively, missing three of four shots and all three 3-point attempts and had no assists to finish with two of his 30 points in the fourth.

But Harden found other ways to help his team win on this night with improved defense. The Warriors shot 44 percent against Harden, who was the most targeted Rockets defender, after shooting 60 percent against him in their two series wins, according to ESPN Stats & Information.

On his two points in the fourth quarter, Harden barked: “Who cares? I mean, we’re a team. We’re really good as a team. So, like I mentioned before, Chris and Eric and Trevor [Ariza], and [P.J.] ‘Tuck’ [Tucker], offensive rebounds, that’s what a team does. They come up in big-time plays. I don’t know how many points I score. Who cares? We won.”

Harden lost in the NBA Finals with the Thunder in 2012. Harden has been eliminated three times in the first round during his six-year Rockets tenure, including in 2016 against the Warriors. Harden and the Rockets lost in five games to the Warriors in the 2015 Western Conference finals. Harden struggled mightily offensively when the Rockets were eliminated in a deciding Game 6 at home in the second round of the 2017 NBA playoffs against the San Antonio Spurs.

Perhaps those postseason shortcomings are the reason that Harden is so serious now. Losing puts more focus on your dream. And for Harden, that dream is for the greatest prize of them all in an elusive NBA championship.

“We came an extremely long way, and we’ve been talking about it all season long in the summertime, put ourselves in the best position, and we’re doing that. So, another opportunity in Game 5, we’ve got to come out and take advantage of it. Simple,” Harden said.

CORRECTION: This article originally stated the Spurs beat the Rockets in Game 5 of the 2017 NBA Playoffs. It has been updated to reflect the correct information.