A.J. Jenkins San Francisco 49ers preseasonThe fans at Candlestick Park got a good look at what Colin Kaepernick has been doing in practice for weeks. There was precision passing along with a scramble to convert on 3rd-and-2, and the 49ers came away with a field goal. Kaepernick’s day ended there, and the rest of the 49ers got to show what they can do.

The 49ers’ defense was very good in the preseason opener, a 10-6 win for Denver. The Broncos only gained 3.3 yards per play and their only points offensively came on a 46-yard field goal in the fourth quarter. Jim Harbaugh seemed happy with the play of the secondary, an unsettled group for the team as they head into the 2013 season. The 49ers were also able to get pressure on the quarterback at times, with Aldon Smith giving Peyton Manning a scare in the lone series for both players.

San Francisco’s offense was ineffective after Kaepernick left, and committed four turnovers in the first half (a D.J. Harper fumble near the 49ers’ goal line resulted in the game’s only touchdown). Apparently the moral of this game was this: what you see in practice is what you get. The backup quarterbacks have only been so-so this offseason, and that continued on Thursday night.

Colt McCoy completed 3-of-7 passes and threw an interception before leaving with what he termed a “stinger” in his shoulder. He’ll get an MRI tomorrow, but didn’t think it was too serious.

Scott Tolzien got the bulk of the time behind center and didn’t do much with his snaps, completing 15-of-26 passes with an INT. I asked Harbaugh what he thought of Tolzien’s performance:

“Some good, some could be better,” Harbaugh said. “It was a good opportunity for Scott to get that action.”

As we trend negative for a bit (this post will end with nothing but positives, don’t worry), there’s no better place to focus our attention than on embattled wide receiver A.J. Jenkins. Harbaugh mentioned earlier in the week that last year’s first round pick needs playing time, and Jenkins got a lot of reps against Denver. The numbers: three targets, one catch for 11 yards … and a lost fumble on said catch. Jenkins turned upfield and saw daylight, but Broncos safety Duke Ihenacho stripped the ball from behind.

Harbaugh’s assessment of Jenkins’ effort was almost the same in terms of words used to describe Tolzien’s night. But the way Harbaugh said, “could’ve been better” sounded a bit worse when talking about Jenkins.

The backup offensive line played poorly, especially compared to the 49ers’ starting linemen, which is to be expected. It would be surprising if Patrick Omameh stuck around much longer, as he seemed to spend more time looking for guys to block than actually blocking. But there were good signs during this game! Some players took advantage of their opportunities, starting with a few rookies.

Corey Lemonier San Francisco 49ers preseasonStock rising

— Corey Lemonier didn’t register any tackles or sacks, but he pressured the quarterback a couple times. People are starting to call the third rounder out of Auburn “Mini Aldon,” a nickname that might stick.

— Vance McDonald was the leading receiver in this game, with four catches for 66 yards. He also made a nice block in space.

“He caught the ball in traffic a couple of times. He was running good. A lot of room for improvement, but I thought it was a good first start for Vance,” said Harbaugh.

— Eric Reid didn’t play with Donte Whitner, and he didn’t get to face Manning, but he has to feel pretty good about his first preseason game. Reid made two notable hits in the contest among his five tackles, and was happy to finally get to feel the crunch of pads on pads.

“I like contact … it was exciting to hit somebody else, to really hit somebody else,” said Reid, whose teammates let him know what they thought of his first big collisions.

“They were giving me a hard time, that’s how we play around with each other. Ahmad told me I need to get in the weight room, I should’ve hit him harder. But I thought it was a good, safe, legal hit so I’m happy,” Reid said.

— Kassim Osgood had three catches for 34 yards and made a couple tackles on special teams, including one that pinned Denver back on their own 5-yard-line.

“Kassim did a great job on the open field tackle on kickoff. He had a tough catch on the boundary on offense. Played with a lot of energy. Looked good,” Harbaugh said.

— Perrish Cox was the only 49er to return a punt, and that return went for 15 yards. He also had a nice 33-yard kickoff return and broke up a pass.

— Nnamdi Asomugha was a willing tackler in limited time.

— Michael Wilhoite played a lot in this game, and Harbaugh praised the middle linebacker for how he communicated and handled the huddle. With Patrick Willis out with a broken hand, Wilhoite has some big shoes to fill.

“Pat obviously does it better than anybody in the world, so now I’ve got to step up to the plate and try to match it,” said Wilhoite, who spoke about how Willis helped him throughout the game.

“I came to the sideline a couple times, looked for him. A couple times I came over, he looked for me. He would just see things that I could do better, see things that I could do faster. He’s always doing that, though. He does it in practice, he does it in the meetings, on the field.”

Nick Moody left with a hamstring injury, which could help Wilhoite’s chances of becoming the team’s No.3 inside linebacker behind Willis and NaVorro Bowman.

— Lawrence Okoye got his first action. Since we’re sticking with the positives in this section, that’s all I’ve got on Okoye.

— Here’s a photo of my view as I walked through the Candlestick Park parking lot this afternoon, since it’s a sight we won’t see many more times.

Candlestick Park 2013 49ers preseason