On this first night of the exhibition season, Denver displayed the opportunistic defense the 49ers lived by the last two years — the very ball-hawking style that carried San Francisco back to the Super Bowl in February after a 17-year wait since its fifth championship.
The NFC champion Niners? They looked sloppy in all phases in 10-6 loss Thursday night.
"You have four turnovers and you win every time," said safety Mike Adams, who contributed a timely interception. "That's what you want to do. As a defense, you want to set the tone, and give the offense a boost. When you get turnovers like that, that's the way it's going to go for you."
A Super Bowl preview in August? Hardly looked that way.
Shaun Phillips scooped up D.J. Harper's second-quarter fumble and returned it 9 yards for the game's lone touchdown. Adams read Colt McCoy's eyes, and jumped in the passing lane for the interception as the Broncos began anew following that stunning double-overtime loss to the eventual Super Bowl champion Baltimore Ravens back in January's AFC divisional playoffs.
Executive John Elway has vowed the playoff disappointment will fuel his team.
With the star quarterbacks on either side — Broncos veteran Peyton Manning and third-year pro Colin Kaepernick — playing all of one series each, it was impossible to gauge just how good their given offenses will be.
This truly was a typical preseason opener for what many consider the best two teams in the NFL; San Francisco and Denver are 1-2 in the AP Pro32 NFL power rankings.
Now, everybody realizes that if they were to play a meaningful matchup it could really be something.
"Offensively, we have work to do," Harbaugh said. "Turning the ball over four times, it's pretty hard to win a game when you're doing that."
Kaepernick completed all four of his passes, two to Anquan Boldin in his 49ers debut after being acquired in a trade from the Ravens. Manning was 2 for 4 for 13 yards.
The 49ers kicked off their "Farewell to Candlestick" season before they move into their new stadium next to team headquarters in Santa Clara in 2014. Fittingly for nostalgia's sake, sprinkled among those suddenly top-selling No. 7 Kaepernick jerseys were some tributes to the old-school favorites: Joe Montana, Jerry Rice, Ronnie Lott.
New 49ers kicker Phil Dawson made field goals of 32 and 38 yards, but missed wide left on the final play before halftime with the flags whipping on a cool summer evening by the bay.
Kaepernick begins his first full season as the starter after taking the job from Alex Smith last November and leading San Francisco to the Super Bowl. And the Niners head to Kansas City for next Friday's game — against the Chiefs' new play caller, Smith.
A.J. Jenkins, one of Kaepernick's key targets, had a forgettable preseason debut.
Jenkins faces high expectations after the first-round pick went without a catch in his highly scrutinized rookie season. The 49ers are depending on him to produce while top 2012 wideout Michael Crabtree spends much of the season recovering from surgery on his torn Achilles' tendon, and Mario Manningham works back from knee surgery.
Only two plays after Phillips scored midway through the second quarter, Jenkins caught an 11-yard pass from Scott Tolzien and fumbled. Denver's Rahim Moore recovered.
A pass by McCoy intended for Jenkins late in the first half was well overthrown and strong safety Adams easily grabbed the interception against his former team.
"We created a lot of turnovers last year, and it's another good start from that standpoint tonight," Manning said. "Different guys, young players, making huge plays. As an offense, you always like to see the defense out there, creating turnovers. Usually that's going to mean really good field position."
49ers first-round draft pick Eric Reid had six tackles in his professional debut.
Broncos backup quarterback Brock Osweiler completed his first six passes and went 13 for 18 for 105 yards.
Notes: The referee and other officials tested headsets for a possible future communication system that would improve the flow of information between officials. ... Former San Francisco RB Roger Craig served as honorary captain as the 49ers began a top-10 countdown of Candlestick moments. ... New Broncos WR Wes Welker was targeted once during Denver's opening series. ... McCoy injured his right, throwing shoulder and will have an MRI exam Friday. Teammates S Bubba Ventrone hurt a hamstring and LB Nick Moody injured his knee.