SAN ANTONIO -- Forcing the pace and making shots in bunches is Houston's calling card this season, but few outside the Rockets' inner circle believed they could impose their will and play as well against the San Antonio Spurs as they did Monday in Game 1 of the teams' Western Conference semifinal playoff series.

Now the call to arms for Houston is to be able to duplicate that performance often enough to win three more times against the Spurs, which will be a tall task indeed.

Trevor Ariza scored 23 points, and James Harden added 20 points and 14 assists as the Rockets jumped on San Antonio in the opening minutes and rolled to a 126-99 victory at the AT&T Center.

Game 2 of the best-of-seven series is Wednesday in San Antonio before Games 3 and 4 are played in Houston on Thursday and Saturday, respectively.

The Rockets led by 11 after the first quarter, by 30 at halftime and by 29 at the end of the third quarter, after which Harden and Ariza were removed from the game.

"We are going to have to be in sync and focused like this in every game," Harden said. "San Antonio is a veteran team, and they are capable of getting hot at any moment. I have to limit them. We were just taking what their defense gave us.

"It was important for us to get off to a really good start, especially on the road, and our energy level was up and we were very active."

Houston reserve center Nene was ejected at the end of the third quarter after a verbal altercation with San Antonio's Dewayne Dedmon. Dedmon was later ejected as well.

Houston's 22 made 3-pointers were a playoff high for a San Antonio opponent. The Rockets' starters outscored the Spurs' first-line players 77-44 in the first three quarters.

"You have to play like a champion, and that's what we did today -- that's just one day," Rockets coach Mike D'Antoni said. "We need to repeat this three more times. We were locked in and competed well. Our defense was good, and we hit some shots. We don't expect this to be like this always, but we needed to defend and rebound like we did tonight."

Clint Capela added 20 points and 13 rebounds for the Rockets. Ryan Anderson scored 14 points, Lou Williams had 13 and Eric Gordon contributed 11.

Kawhi Leonard led the Spurs with 21 points and 11 rebounds. He also sat out the fourth quarter with no hope that San Antonio could mount a comeback.

Tony Parker and Jonathon Simmons added 11 points apiece, but San Antonio got only four points and six rebounds from LaMarcus Aldridge and eight points from Danny Green, all in the third quarter when the Spurs were already well behind.

"We really have to step up, and it's hard to pinpoint something because we got outplayed in just about everything," Spurs guard Manu Ginobili said. "We were not ready or attentive, and they were inspired -- they played great. They made shots early, and then their confidence level went way up. We started to get a little frantic and things snowballed."

The Rockets came out of the gate full of energy and hit six of their first eight shots and five of their first 11 from beyond the arc to assume a 28-13 lead with 3:05 to play in the first quarter.

The Spurs responded with an 8-0 run, capped by 3-pointers from Patty Mills and Leonard, to crawl within 28-21. But Houston scored six of the final eight points of the quarter and led 34-23 after 12 minutes.

Houston opened the second quarter in a 15-2 run in the first 3 1/2 minutes that stunned San Antonio and buried the Spurs in a 49-25 hole.

The Rockets' lead grew to as many as 30 points in the waning moments of the second quarter and hit that margin again at the half when they led 69-39.

If the Spurs were going to get back in the game, they needed to do some damage in the first half of the third quarter. Instead, Houston just toyed with San Antonio as Capela had three dunks off Harden assists in the first 5 1/2 minutes of the quarter to help push the Rockets' advantage to 80-45.

"We competed, but I don't think we executed in a very wise manner," Spurs coach Gregg Popovich said. "We disobeyed a lot of basic basketball rules that they took advantage of. If we are going to shoot quickly and shoot poorly, it's going to be a fastbreak deal all night long, and they are better at that than we are."

NOTES: The Rockets are in the postseason for the 30th time in 50 seasons. Houston has landed spots in the postseason in 10 of the past 14 seasons, including five straight, after missing the playoffs in three straight seasons from 2009-10 through 2011-12. ... San Antonio's current playoff berth is its 20th straight, which is the longest active streak in the NBA (the second longest is Atlanta with nine). ... The Rockets' win at Oklahoma City in Game 4 of the first round in this year's playoffs snapped a seven-game road losing streak in the postseason (six were to Golden State in 2015 and 2016). ... The Spurs are the only team in the 2017 NBA playoffs with two NBA Finals MVPs on their roster, G Tony Parker and F Kawhi Leonard. Parker was awarded the honor in 2007, and Leonard received the award in 2014.