SAN FRANCISCO – Here are five things to watch in San Francisco on Friday night.

1. Tight end Jared Cook – The Packers’ most notable free-agent addition in recent years will be getting his first in-game snaps with QB Aaron Rodgers, for however long the first unit plays. Cook and Rodgers have looked on the same page from the first day Cook practiced in camp, so there’s no reason for concern, but if there’s a veteran to keep an eye on, Cook’s the one.

2. The rookie draft picks on the offensive line – Second-rounder Jason Spriggs learned some valuable lessons against Oakland’s Khalil Mack last week, while sixth-rounder Kyle Murphy made a solid debut after missing two weeks of camp due to a concussion. The follow-up performance for both will be important.

3. Defensive tackle Christian Ringo – With Mike Daniels and Kenny Clark both missing time this week, Ringo moved up the depth chart in practice and could get a lot of playing time against the 49ers. The practice-squad holdover had a sack in the first preseason game but has been relatively quiet since. He could use a big night.

4. Fullback Aaron Ripkowski – The improvement in Ripkowski’s lead blocking from the first game to the second was evident, and if Mike McCarthy continues his preseason commitment to running the ball, Ripkowski should get plenty of work.

5. The young cornerbacks – Josh Hawkins had an interception and long return against the Raiders. Makinton Dorleant practiced well this week. Robertson Daniel and LaDarius Gunter would love to add a splash play to their body of work. Lots of young talent battling it out here.