2-minute drills favors defense

The 49ers finished the afternoon practice with a live-action 2-minute drill, always an antidote to the doldrums of camp. It’s just that things didn’t go too well on the offensive side of the ball.

Here’s the setup: Offense takes over on its own 38-yard line 1:25 left.

To start, the first-team O went against the second-team D. Alex Smith’s unit picked up a first down and Smith spiked the ball to stop the clock, making it second down. Then things unraveled: TE Delanie Walker false started. Smith fired a pass quickly to WR Ted Ginn, who was matched against S Taylor Mays wide right, but Ginn wasn’t looking for the ball. On third-and-15, Smith’s protection broke down and he missed RB Anthony Dixon short. On fourth-and-15, Smith stepped up in the pocket and overshot Ginn across the middle in traffic.

Nate Davis’ second unit (yes, you read right) had a very similar experience against the third-team defense. The No. 2s also netted one first down. Then came four straight incompletions: Davis throwing away as DT Khalif Mitchell touched him, Davis leading WR Kevin Jurovich out of bounds, Davis unloading to Michael Robinson under pressure and the RB not looking, Davis overshooting Jurovich deep.

Would’ve hated to see what happened with the first-team defense on the field.

Other notes and obsevations from the p.m. practice…

• G/T Adam Snyder has a concussion. He becomes the fourth 49er to suffer a head injury this August, following C/G David Baas, Walker and OLB Travis LaBoy. Snyder was at practice, and seemed to be in no distress.

• TE Nate Byham was sick and did not practice. TE Vernon Davis (knee), OLB Brandon Long (knee) and WR Kyle Williams (toe) also sat out. Veteran courtesy for RB Michael Brian Westbrook, LBs Patrick Willis and Takeo Spikes, DE Justin Smith and S Michael Lewis.

• Rookie ILB NaVorro Bowman was making some noise. He made a great play in 7-on-7, running with Walker and reaching up to knock away Smith’s pass. And a little later he was in the backfield to tap Frank Gore down in team period.

• Maybe just a coincidence, but TE Tony Curtis was around the end zone a lot today. He reached back and caught a touchdown pass from David Carr in 7-on-7, but Smith missed him at the goal line a couple snaps later.

• Walker turned in a one-handed catch on a sideline throw from Carr. The tight end has quietly put together a strong camp.

• Looked like Cody Wallace was at center with the second-team O-line late in the day, while Tony Wragge was at LG. Baas continues to get all the first-team reps in Eric Heitmann’s absence. Not sure what the deal is with Wragge, who was supposed to compete to be Heitmann’s stand-in.