Kevin Durant (below) and the Thunder head back to Oklahoma City for Game 6, where they’ve won nine straight over the Spurs. (Ronald Martinez/Getty Images)

In the end, it really didn’t matter whether Gregg Popovich was going to change his starting lineup, Tony Parker was going to be more aggressive or the San Antonio Spurs were going to regain their impeccable ball movement and accuracy from three-point range. In a bizarre Western Conference finals in which momentum is only on the side of the team playing in its building, the only adjustment San Antonio had to make against the Oklahoma City Thunder for Game 5 was to slip on its white jerseys.

The Spurs throttled the Thunder, 117-89, in a lopsided performance that was eerily similar to the first two games of this series to move one victory away from making their sixth NBA Finals. But if they have any plans of finishing the series in six games on Saturday, that would require winning on the road — something that neither team has been able to do in a Western Conference finals that has yet to yield one competitive game.

“It’s the craziest series I’ve ever been involved in,” said Tim Duncan, 38, a four-time NBA champion who is playing in the 44th postseason series of his career.

For the second straight game, Duncan spent the fourth quarter watching from the bench. But unlike the Spurs’ Game 4 blowout loss, in which he sat, hunched over, disgusted and resting up, Duncan repeatedly got out of his seat to celebrate the romp.

Duncan had already done his job by scoring 22 points and grabbing 12 rebounds to take another step toward avenging a disappointing loss to the Miami Heat last June. Manu Ginobili added 19 points and Parker chipped in with 12 points and four assists.

The Spurs and Thunder finished with the best road records in the NBA, but they have taken turns getting embarrassed on their opponent’s floor in this series. Kevin Durant scored a game-high 25 points and Russell Westbrook had 21, but the Thunder will have to hope that the home trend continues as the series heads back to Chesapeake Energy Arena, where San Antonio has lost nine straight.

The Spurs won the first two games of the series at home by a combined 52 points. Then the series shifted to Oklahoma City. There, Serge Ibaka returned from a strained left calf that was supposed to keep him sidelined for the rest of the postseason but only cost him the first two games. Thunder Coach Scott Brooks also inserted Reggie Jackson into the starting lineup along with Ibaka to give his team more scoring punch.

That resulted in Oklahoma City handily winning the next two games, eliciting flashbacks of the conference finals in 2012, when the Spurs won the first two games and the Thunder won the next four.

“It’s interesting. You really can’t explain it because both teams are really good and both teams compete, but it’s the way it is,” Thunder Coach Scott Brooks said of the five blowouts. “We have to regroup and come back better in a few days.”

On Thursday, instead of being spooked by the shot-blocking presence of Ibaka or withering under the relentless pressure of Westbrook, the Spurs attacked the Thunder on nearly every possession. The Spurs made 13 three-pointers, shot 51.3 percent from the field and attempted 30 free throws.

“We just played harder,” Popovich said. “You know, you play with passion. You play with determination. It seems kind of a trite sort of notion, but sometimes players do, and sometimes they don’t.

“They’re human beings. They’re not automatons.”

Before Game 5, Popovich was coy about his plans to change the starting lineup and stated only that it would “probably not” be the same. Popovich made the somewhat surprising decision to go with the sparingly used Matt Bonner in place of power forward Tiago Splitter.

The move did little to slow down the Thunder early in the game. Jackson made his first five shots and scored 11 points in the quarter, and Westbrook put Oklahoma City ahead 26-19 when he drove left around Kawhi Leonard and threw down a ferocious one-handed jam.

But the Spurs closed out the period on a 13-6 run and entered the second period tied at 32. The teams have been able to stay close for only one quarter before the home team eventually goes on a run.

For the Spurs, that began when Duncan made a tip shot to put the Spurs up 37-35. San Antonio never trailed again.

Parker was severely outplayed by Westbrook in Oklahoma City, overwhelmed by the tenacity of the Thunder’s fiery point guard. In Game 4, Westbrook joined Michael Jordan as the only players to have a game with 40 points, 10 assists, five rebounds and five steals in a playoff game.

The Spurs have remained a championship contender as Duncan got older because of Parker, and they had no chance of making a return trip to the Finals if their all-star point guard remained passive and ineffective. Parker didn’t have to score a lot, but he made back-to-back jumpers to put San Antonio ahead 48-40, forcing Brooks to call a timeout, and Duncan converted a three-point play to extend the lead to 51-42.

Durant threw down an alley-oop dunk on a pass from Westbrook to bring the Thunder within six, but Oklahoma City got no closer.

“We’ve just got to worry about the next game. We’re guaranteed 48 more minutes,” Durant said. “It’s been an up-and-down series, but we’ve got to find a way to come with it in Game 6.”