PORTLAND, Ore. -- The San Antonio Spurs continue to show the Portland Trail Blazers what championship-level basketball is all about.

Guard Tony Parker scored 20 of his 29 points in the first half as San Antonio whipped Portland 118-103 on Saturday night at the Moda Center.

Forward Tim Duncan collected 19 points, seven rebounds and four assists for the Spurs, who took a 3-0 lead in the Western Conference semifinal series. San Antonio can wrap up the best-of-seven series with a win on Monday night.

"The close-out is always the hardest game," said Parker, who made 12 of 20 shots from the field and also had six assists. "We know Portland is going to come out and play with a lot of motivation. (The Blazers) have nothing to lose.

"I'm sure they want to win a game in front of their hometown. We're going to have to match their energy, but it would be great to get it and get a rest."

The Spurs trailed for 17 seconds -- when Portland led 13-12 in the first quarter -- in Game 3. The Trail Blazers have led for less than 33 total seconds in the three games thus far.

"We're just playing great right now," Parker said. "We're very focused."

Five players scored in double figures for San Antonio, including forward Kawhi Leonard with 16 points, guard Manu Ginobili with 14 and guard Patty Mills with 10.

Four players scored 20 or more points for the Trail Blazers. Guard Wesley Matthews led the way with 22. Guard Damian Lillard and forward LaMarcus Aldridge each had 21 and forward Nicolas Batum had 20 to go with nine rebounds and seven assists.

As in the previous two games, San Antonio jumped to a double-digit lead early and led 60-40 at halftime.

"It's frustrating," Portland coach Terry Stotts said. "We're playing a championship-caliber team. You look at the scoreboard and you're down 20. It's a hole that's hard to dig out of."

San Antonio has posted four straight lopsided victories since beating Dallas 119-96 in Game 7 of their first-round series.

"This is well as I've seen (the Spurs) play all season," Stotts said. "They came out of the gate in Game 7 against Dallas and they haven't stop since."

Parker was the driving force, taking command on offense and helping force Lillard into a 7-for-21 shooting performance at the other end.

"Tony has been the engine for us," San Antonio coach Gregg Popovich said. "He started out really well tonight. He made shots, he involved everybody else, he played great 'D.' He's playing a complete game."

The Blazers used a 10-2 run to go in front 13-12 early, but it was their only lead. The Spurs regained control, finishing the quarter on a 16-5 tear to take a 28-18 advantage into the second quarter. Parker had 12 points on 6-for-8 shooting from the field in the quarter.

The Spurs stoked the lead to 58-35 late in the second quarter and took a 20-point advantage into intermission.

Portland made a run in the first five minutes of the third quarter, outscoring San Antonio 17-4 to draw within 64-57. The Spurs righted themselves to go back in front 72-60 and carried an 83-69 advantage into the fourth quarter.

When Parker and Leonard converted back-to-back three-point plays, San Antonio's lead was 103-81 with 7:43 to play and the Blazers seemed in big trouble. Portland scored the game's next 10 points to cut it to 103-91 with 5:46 on the clock, but it was as close as the Blazers would get.

"They never stop playing," said Aldridge, who had a game-high 12 rebounds but was only 9 for 23 from the field. "You guard their first option, they go to the second. You stop the second, they go to the third. They're persistent.

"They're going to run their stuff over and over, and once you mess up, they're going to make you pay. Tonight, they did that. They play championship basketball. It's what we have to get to."

NOTES: The Spurs shot 48.3 percent from the field and were a franchise-playoff record 25 for 25 from the foul line. It was the first time a San Antonio team has not missed a free throw in a playoff game. ... San Antonio scored 17 points off 10 Portland turnovers in the first half; the Blazers scored no points off the Spurs' giveaways. ... The Spurs had a 40-6 advantage in bench points. For the series, the difference is 140-43. ... The Trail Blazers were without sixth-man G Mo Williams, out with a strained groin. ... Before Thursday's Game 2 at the AT&T Center in San Antonio, Blazers F Thomas Robinson found a snake in his locker. Did the Spurs find any animals in their locker room at the Moda Center before Saturday night's game? "No," Popovich said, "but we were expecting a beaver." (Oregon is the "Beaver State," and the beaver is the mascot at Oregon State University.)