PORTLAND, Ore. -- Noah Vonleh was as surprised as anyone when the ball wound up in his hands as the final seconds ticked down Monday night at Moda Center.

Vonleh, sensing time was of the essence, went up for a layup as the clock expired, and he gave the Portland Trail Blazers a 99-98 victory over the San Antonio Spurs.

Shabazz Napier scored a career-high 32 points for the Trail Blazers (41-40), who won their third straight game and ninth in their past 11 outings.

Kawhi Leonard scored 18 points for the Spurs (61-20), who lost their third straight.

All five starters scored in double figures for Portland, including Evan Turner with 16 points, Pat Connaughton with a career-high 15, Meyers Leonard with 13 and Vonleh with 12 to go with 11 rebounds.

The final scenario was set up after Jake Layman's dunk closed Portland to within 98-97 with 12.3 seconds on the clock.

After a San Antonio turnover, the Blazers called timeout with six seconds left. Coach Terry Stotts drew up a play for Napier off a mid-pick-and-roll with Leonard. Napier was stripped as he drove to the basket. The ball got knocked off Leonard's knee into the hands of Vonleh, who put the ball in the basket just before the horn sounded.

"Somehow the ball happened to fall into my hands," said Vonleh, who made 6 of 9 shots from the field. "I just just trying to get it up quick. I didn't know how much time was left."

"We call that our 'double-knee play,'" Stotts joked. "We knew there was enough time for all of that to happen."

The Spurs were just as stunned at the turn of events as the Blazers.

"The ball was just fumbling around, and it ended up in (Vonleh's) hands," said forward LaMarcus Aldridge, who had 12 points in 18 minutes. "They had the guy in the right place at the right time, and they got the win."

With the No. 8 playoff seed in the Western Conference sewed up, the Blazers rested three starters, including point guard Damian Lillard. That opened the door for Napier, who was 9 of 20 from the field -- including 4 of 7 from 3-point range -- and 10 of 11 from the foul line. The third-year player also had six rebounds and five assists while playing a career-high 37 minutes.

"I was really happy for the young guys who got to play and made the most of their opportunity," Stotts said. "Shabazz did a nice job of directing the team and scoring. He got a little gassed out there, but he was carrying us."

San Antonio trailed only 47-43 at halftime despite 3-of-18 shooting in the second quarter.

The Spurs went on an 8-0 run to go ahead 65-60 midway through the third quarter. The difference was 76-71 heading into the final period.

Napier tied it at 81-81 on a pair of foul shots, then scored on a drive to give the Blazers an 83-81 edge with 5:33 to play. Jonathan Simmons answered with a layup to tie it at 83-83 with 4:26 remaining.

After a pair of David Lee free throws, Napier evened the count at 85-85 on a jumper with 3:49 to go. Dewayne Dedmon's hook shot pushed the Spurs ahead 87-85, but Napier bombed in a 3 to make it 88-87 with 2:30 left.

Bryn Forbes' 3-pointer gave San Antonio the lead back at 90-88 with 2:16 remaining. Simmons followed with a dunk to make it 92-88.

Napier made three free throws to get Portland to within 92-91 with 1:44 to play. Simmons' windmill dunk pushed the Spurs on top 94-91 with 1:30 left. Kyle Anderson scored on a drive and it was San Antonio 96-91 with 1:17 to go.

Connaughton nailed a jumper to close it to 96-93, and Vonleh's follow shot make it 96-95 with 35.8 seconds left.

Forbes made two foul shots to up the Spurs' advantage to 98-95 with 18.2 ticks left, setting up the frenzied final seconds.

NOTES: Portland rested starters G Damian Lillard, G CJ McCollum and F Moe Harkless, and reserve G Allen Crabbe (foot) sat for his second straight game. ... Lillard and McCollum both said they expect to play in Wednesday's regular-season finale against New Orleans. ... It was the Blazers' eighth straight win at home. ... Portland coach Terry Stotts said C Jusuf Nurkic will be medically evaluated Friday for the non-displaced fracture on his right leg. Does Stotts expect Nurkic to be able to go in the Blazers' playoff opener at Golden State? "I have no idea," he said. ... Coach Gregg Popovich on F LaMarcus Aldridge's second season with the Spurs: "He's had a really good year. He's more confident. He's shooting the ball and not just deferring to (teammates) and trying to fit in. He's being aggressive, and that's what we want from him. He's really worked hard on his defense and made a second effort on the boards."