A two-year starter at left guard, Martin transitioned to center his final season at USC before announcing early for the NFL draft.
The third-round pick is now taking second-team reps at the position and is receiving praise from Coach Jim Harbaugh.
“Marcus Martin had a very good game, a very physical game,” Harbaugh told 49ers.com.
“I was just excited to get the opportunity to play that many snaps,” Martin said.
San Francisco, 0-2 in the preseason, will host the San Diego Chargers on Sunday.