SAN ANTONIO — Game 4 of the Western Conference finals had already gotten out of hand Tuesday. The momentum in the series had already swung.

For 31/2 quarters of Oklahoma City's 105-92 victory, Russell Westbrook bullied the Spurs, when Serge Ibaka wasn't spooking them entirely. Kevin Durant was flexing his MVP mojo.

Finally, Cory Joseph had seen enough.

The Spurs' 6-foot-3 third-string point guard, making his first significant appearance of the series, rose and threw down his second career dunk. Right on top of Ibaka.

“He's a great shot-blocker, so if he blocked my shot, so what?” Joseph said. “I just went for it.”

In one too-little, too-late moment of standing up to the Spurs' personal boogeyman, Joseph demonstrated how his team must play, now that the series is tied headed into a pivotal Game 5 on Thursday night at the AT&T Center.

Just go for it.

Coach Gregg Popovich made the point to his team after a grisly Wednesday afternoon film session.

“I actually told the team, 'Everybody has to take on the attitude of Cory Joseph — kind of a take-no-prisoners, bunker attitude,'” Popovich said. “He did that better than anybody on our team.”

Joseph scored 11 points in 17 minutes after Popovich cleared his bench and played with a fearlessness the Spurs can use with the series against OKC teetering.

He also played largely within himself, which is also a key. The Spurs aren't going to out-athlete the strapping Thunder, Popovich said, so they must out-execute them.

“There's no way we can match their athleticism,” Popovich said. “So we have to play smart.”

For the second time in three postseasons, the Spurs grabbed a 2-0 lead on the Thunder in the Western Conference finals, touched down in OKC and promptly lost their identity.

The artistic ball movement that typified their two victories, earned by a total of 52 points, stopped. The Spurs committed only 13 turnovers in Game 4, but 12 were live-ball steals by the Thunder. Those, combined with eight blocked shots, fueled a 21-0 edge for OKC in transition points.

Westbrook ended with 40 points, 10 assists, five steals and five rebounds, at times overwhelming Tony Parker, his Spurs All-Star counterpart. Durant scored 31 points, and the Spurs return to San Antonio feeling a bit the way the Thunder did when they last left the AT&T Center.

Then, OKC faced doubts after suffering the worst postseason defeat in club history.

“I was disappointed that we didn't play the way we were capable of playing,” OKC coach Scott Brooks said.

There are no easy answers now that the script has flipped, especially with Ibaka — out for the first two games with a calf injury — back to menacing the Spurs' offense as he did during the regular season.

The Spurs have lost 12 of the last 14 against OKC with Ibaka in uniform.

“We've got to be way smarter and sharper,” guard Manu Ginobili said. “If we let them push us around and we're not strong with the ball, that's where they get us on our heels. We know we've got to play the game to perfection.”

Pulled midway through the third quarter Tuesday, the Spurs' starters got a lesson in that from their bench cohorts.

Led by Joseph and forward Boris Diaw, the Spurs' reserves mounted something of a charge in the fourth quarter, cutting a deficit that had ballooned as high as 27 to 12.

Tim Duncan, the Spurs' captain, departed OKC hopeful the strong finish from the team's second unit might point the way back on top in the series.

The trick now will be for the Spurs to recreate Tuesday's fourth quarter Thursday, this time using their starters, and against an OKC team that had not already punched cruise control.

“I don't know what it is,” Duncan said, “but we have to fix it quick.”

Popovich made clear the most impactful changes the Spurs can make for Game 5 will be mental.

“It doesn't matter what we do tactically if we don't up that determination,” Popovich said, “that persistent, aggressive, ugly, hard-nosed attitude.”

In one otherwise inconsequential play late in Game 4, Joseph showed the way. It is up to the rest of the Spurs to follow him.

jmcdonald@

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Twitter: @JMcDonald_SAEN