DENVER -- In what could be the final preseason tune-up for the starters, the Broncos delivered on Sunday.

In three drives, quarterback Peyton Manning led the offense to a 17-0 lead, and quarterback Caleb Hanie closed the first half with a touchdown throw to give the Broncos a 24-10 halftime lead.

By the end of the afternoon, however, the Broncos had fallen to the San Francisco 49ers 29-24 at Sports Authority Field at Mile High.

"I'm never really happy losing ever, but I thought our firsts looked pretty sharp and I think we made great strides this week," Head Coach John Fox said.

Manning got the offense going early, stringing together an eight-play drive that culminated in a 53-yard Matt Prater field goal. From there, he completed his next eight passes for 86 yards over his second and third drives, both of which ended with touchdown passes to wide receiver Eric Decker.

On his first scoring drive, which spanned nine plays, Manning hit Lance Ball on a pass that landed right in the running back's arms down the sideline for a 38-yard gain, even as the quarterback was hit hard by 49ers linebacker Parys Haralson. On the very next play, Manning hit McGahee for a 14-yard gain. Two plays later, Manning found Decker in the end zone for a 10-yard touchdown -- his first as a Bronco.

The signal caller's work was done after giving the Broncos a three-possession lead. He completed 10 of 12 passes for 122 yards and two touchdowns. He left the game with a quarterback rating of 148.6.

"I don't think there is really any barrier with this offense," Manning said. "I thought it was good that no matter what group that we were in, we showed that we can move the ball against a good defense. Once again, it's just preseason, but I think we can build off some of those things."

The first-team defense held up its end of the bargain as well, limiting the 49ers to just 83 yards and three first downs -- compared to Denver's 16 -- in the first half.

Defensive end Elvis Dumervil notched a sack, linebacker Joe Mays laid a big hit on quarterback Alex Smith and Wesley Woodyard recovered a fumbled snap on the very next play, which set up Manning's second touchdown pass.

"Everything was kind of going our way," defensive lineman Derek Wolfe said. "The ball was falling in our hands and it was going great. There is nothing better than whenever you game plan and then execute that gameplan. That's kind of what happened – we executed what we were practicing all week."

Despite being held to just 14 rushing yards, San Francisco did score 10 points in the half. First, Smith hit tight end Vernon Davis for a 44-yard touchdown on a one-play drive after Denver was penalized for illegal touching on a surprise onside kick.

Next, on Hanie's first drive, he was intercepted by 49ers cornerback Perrish Cox, who returned the ball to the 19-yard line.

Denver's defense stood tall, however, forcing a three-and-out and San Francisco settled for a David Akers field goal to pull the score to 17-10.

Hanie bounced back at the end of the half, putting together a 12-play, 73-yard drive that he capped off with a 5-yard touchdown strike to tight end Joel Dreessen.

"It was a well-executed first half," Decker said. "I thought both offensive and defensively we felt comfortable with what we did on the field. We're going to go in and watch film, correct what we need to and just get ready for Arizona and stay healthy for the season."

In the second half, the 49ers scored 19 unanswered points -- a 26-yard touchdown run by running back Anthony Dixon followed by four Akers field goals -- taking the lead at the start of the fourth quarter and never relinquishing it.

The Denver defense had a pair of third-down stops in the red zone -- including a goal-line stop -- to force two of those field goals and keep the 49ers from tacking on more points.

But quarterbacks Brock Osweiler and Adam Weber weren't able to mount any scoring drives. For the young signal callers, the preseason is just as much about gaining experience as grabbing the win.

"Every time I can get that in the preseason, that's only going to make me better as a quarterback in the future," Osweiler said. "I'm just trying to take advantage of every opportunity I'm getting and clean up the mistakes. We just have to score some points."

In just four days, the Broncos take on the Arizona Cardinals at University of Phoenix Stadium to close out the preseason.

Historically, starters don't see much playing time -- if any -- in the preseason finale. So while some thought will go to the regular-season opener against the Pittsburgh Steelers, the club knows there's still plenty to get accomplished in the preseason.

"We know we still have a lot of work to do," Dreessen said. "We're feeling good about things, but we have a lot of work to do."