A few months removed from their first Super Bowl game in years, the San Francisco 49ers hardly looked like a championship-caliber team, dropping a sloppy exhibition game to the Denver Broncos at home, 10-6.

The 49ers, who are ranked first in the AP ProNFL power rankings, had four turnovers and no touchdowns against the second-ranked Broncos. All of San Francisco's points came from field goals, both from Phil Dawson. Dawson opened up the scoring with a 32-yard kick in the first quarter, but it was a Broncos show the rest of the way.

"Turning the ball over four times, it's pretty hard to win a game when you're doing that," 49ers coach Jim Harbaugh told ESPN.

In contrast, Denver's Peyton Manning was happy with his team's defense. "We created a lot of turnovers this year, and it's another good start from that standpoint tonight," he said. However, the Broncos have lost center Dan Koppen for the season due to a torn knee ligament.

The L.A. Times reported that Koppen suffered an anterior cruciate ligament tear during a nine-on-seven workout on Sunday. The eleven-year veteran was replaced by Manny Ramirez, who barely made a dent in Thursday's game.

On the part of the 49ers, they are awaiting the debut of fourth-round pick Marcus Lattimore, who is recovering from a knee injury that left the running back with three torn ligaments. He was projected to be among the top prospects in this year's draft until October, when he suffered the injury while playing for South Carolina.

AJ Jenkins who had a disappointing rookie season also continued to struggle in the preseason. Jenkins caught only one pass of three thrown at him - and fumbled it.

"I've just got to look at the film and see what I've got to work on," Jenkins told the San Francisco Chronicle. "It's the first preseason game of the season so we all have to work on something."

For the rest of the 49ers, Thursday's exhibition was indeed a sign that more work needs to be done. Harbaugh's statement about Jenkins' performance at the postgame press conference said it all.

"Could have been better."