SAN ANTONIO >> Maybe they’ll finally get a challenge this time.

The San Antonio Spurs and Oklahoma City Thunder have simply rolled through this postseason. There’s the 18-game winning streak that has the Spurs flirting with history. Seventeen combined playoff games and just one loss. The Thunder sending home the last two NBA champions, and no other playoff teams besides these two that can boast a series sweep.

What took the Western Conference finals so long to get here Sunday, anyway?

“I think we both deserve it,” Spurs guard Manu Ginobili said.

Few would dispute that.

It’s a clear-cut matchup of the West’s best teams without any qualifiers: No what-if speculating because of devastating injuries like Derrick Rose’s blown-out knee that sunk top-seeded Chicago and reshuffled predictions in the East, nor were there lucky breaks or Game 7 heartbreakers that will gnaw at San Antonio’s and Oklahoma City’s dispatched opponents and their fans all summer.

By and large, the Spurs and Thunder have just steamrolled to this point.

The top-seeded Spurs clobbered Utah and the Los Angeles Clippers by an average of 14 points a game. They’re one victory from tying the 2001 Lakers for the longest winning streak kept alive in a postseason and two from becoming just the fourth team in NBA history to win 20 in row.

“It’s been a while since we’ve been in the Western Conference finals. And it’s been a week kind of sitting here stewing and waiting on it,” said Spurs forward Tim Duncan, whose last playoff trip this far in 2008 ended with a loss to the Lakers. “All of that together makes it an exciting series to start.”

Oklahoma City — which finished three games behind the Spurs for first place — didn’t have as many blowouts the first two rounds as San Antonio but drew tougher matchups. The Thunder avenged falling at the brink of the NBA Finals last year with a sweep of defending champion Dallas, then beat the Lakers in five.

Even before the playoffs, it was arguably easy to see this conference finals matchup coming: From the second week of the regular season until April 6, the Thunder held first place in the West.

Then the Spurs leapfrogged them, and never gave it back.

“I know they’re the No. 1 seed — they’re a tough group, they haven’t lost in a couple months,” Thunder forward Kevin Durant said. “But I think we bring another dimension to the table as well and we come out and compete.”

Then the NBA’s scoring champion the last three seasons added, “We’re a group that’s been together for four or five years. They’ve been together for 15 years. Those guys, they know each other inside and out.”

If there’s any broad way to frame this series, it’s that: the up-and-coming Thunder vs. the old-and-still kicking Spurs. The triumvirate of Durant, All-Star point guard Russell Westbrook and Sixth Man of the Year James Harden are all 23 or younger. Spurs point guard Tony Parker turned 30 last week, while Manu Ginobili is 34 and Duncan 36.

Yet youth hasn’t been served when these teams have played. The Spurs are 8-2 against the Thunder since 2009, including two wins this season despite Ginobili not playing because of injury. The Spurs were the NBA’s best 3-point shooting team this season at 39.3 percent, but they especially picked apart the Thunder from behind the arc, shooting 52 percent in their three most recent meetings.

Durant this week brushed off the Thunder’s troubles defending San Antonio’s slash-and-kickouts that set up so many of those 3-point looks. He also grew noticeably annoyed by questions about how the Thunder will stop the Spurs — “You’ve got to ask me about how we’re going to come at them,” Durant shot back — and was asked before boarding a plane to San Antonio on Saturday whether they’re leaving as underdogs.

“Everybody’s always been using that, ‘We’re too young for this and it’s not our time, we’re not ready,'” Durant said.

The Thunder say they are.

“Our success is just not overnight. It just doesn’t happen,” Thunder coach Scott Brooks said. “It happens through all of the effort that guys put in. This series is going to be the same thing.”

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AP Sports Writer Jeff Latzke in Oklahoma City contributed to this report.