SANTA CLARA -- The 49ers turned their hyped Levi's Stadium debut into a real dud. So bad, in fact, tens of thousands of fans left the snazzy new Silicon Valley digs midway through the third quarter.
Colin Kaepernick was thoroughly outshined by 38-year-old Peyton Manning in Denver's 34-0 rout Sunday, with the San Francisco quarterback going 5-for-9 for 39 yards in his two series.
The 49ers turned the ball over four times and gave up big plays on defense.
"We're off. It's that kind of off right now. It's a little, it's correctable, but it shows up," Niners coach Jim Harbaugh said. "That's football, it punishes mistakes. It rewards execution and precision. That's where we're off right now. We're not a precise team."
Manning threw a 17-yard touchdown pass to Julius Thomas and dominated in his two series to spoil the NFL debut at sparkling $1.2 billion Levi's Stadium.
Major League Soccer's Earthquakes beat the Seattle Sounders in the stadium's first sporting event Aug. 2.
"It's been a good start. That's all it is, though," Manning said. "We've still got some things we have to improve on."
The 38-year-old Manning, beginning his 17th season after throwing for an NFL-record 55 touchdowns last year, completed 12 of 14 passes for 102 yards and a 120.8 rating. He was 8-for-8 on Denver's second drive, then backup Brock Osweiler took over and threw for a score and led another touchdown drive in a preseason matchup of the past two Super Bowl losers.
Demaryius Thomas had three of his five catches on Denver's opening drive, including a 20-yard gain. That gives Thomas 10 receptions for 89 yards in Denver's two victories against the NFC West's powerhouses, the Super Bowl champion Seattle Seahawks and San Francisco.
"He's Peyton Manning. I don't know if there's anything more to say beyond that," Niners safety Eric Reid said.
C.J. Anderson ran for a 1-yard TD, while Matt Prater kicked a 26-yard field goal and Mitch Ewald added a late 22-yarder. San Francisco's typically spot-on Phil Dawson sailed two long kicks wide right.
Denver did it on defense, too, getting two interceptions and a fumble recovery and a goal-line stand to end the game. The Broncos recovered another fumble on special teams.
The 49ers lost safety Antoine Bethea to a concussion early in the second quarter. He was able to walk off on his own, but later left for the locker room.
As San Francisco struggled in all phases, tens of thousands of fans made their way out midway through the third quarter -- certainly helping to alleviate traffic concerns. The 49ers ended a four-decade run at Candlestick Park last season.
"It's nicer than nice. I'd heard a lot about it," Manning said of the new stadium. "Of course it was a great day for football. Beautiful setting, great sight lines for the quarterback on the field. I was very impressed."
Two key members of San Francisco's offense made their first appearances of the preseason, with Frank Gore running for 9 yards on the first of his two carries. Wide receiver Michael Crabtree also appeared as defensive stars Patrick Willis and Justin Smith got the day off.
Kaepernick had his chances during his brief stint on the field.
"We just have to finish our drives off," Kaepernick said. "We just haven't finished the last few plays of the drive."
On third-and-4 from the 37 the first drive, Kaepernick barely overthrew Brandon Lloyd in the end zone. Dawson then missed his first field goal attempt in the new stadium, sending a 55-yarder wide right. He missed wide right again from the other end on a 44-yarder late in the first half, and these weren't in the unpredictable elements of Candlestick.
The 49ers are scoreless in their last seven quarters and have been outscored 57-3 this preseason. They lost 23-3 at Baltimore on Aug. 7.
"It's the preseason, but it all means something," left tackle Joe Staley said. "Scoring points is the name of the game, and we haven't done it. ... It will be a real test this week to see how we rebound from this."
49ers vs. Chargers
WHEN: Sunday, 1 p.m.
WHERE: Levi's Stadium, Santa Clara
TV: KTVU (Ch. 2)
RADIO: KGO (810 AM)