And his experience will be put to good use this week, as defensive coordinator John Pagano will play Marshall at safety in certain packages against his old team, the Arizona Cardinals, in the San Diego's season opener on Monday (10:20 p.m. ET, ESPN). Marshall spent the 2011 season with the Cardinals.
But don't consider this a position change. Other corners such as Charles Woodson have moved to safety as they have gotten older to extend their NFL careers. However, Marshall still is listed as a cornerback behind Brandon Flowers on San Diego's depth chart.
Marshall's expansion of duties provides more depth and versatility for Pagano's defense, with the former Fresno State player's ability to play outside corner, slot defender and in the back end as a safety if needed. Marshall said he was asked by Pagano to learn the safety position earlier in training camp, and then pressed into duty once Jahleel Addae suffered a hamstring injury against the Seattle Seahawks in a Week 2 preseason game.
Addae has not practiced since, and his availability is in question for Monday's contest. Marshall said he played some safety while with the Cardinals, so learning a new position is not something that's truly new.
Marshall said playing safety is somewhat like playing slot defender, something he's done for most of his NFL career.
"It's similar, but it's just the calls that are different," Marshall said. "You got to make the calls. You've got to make the checks. But I did it before in Arizona, so it kind of came quick to me last week during practice, and I've just been rolling with it.
"It's a better opportunity for me just because they know I can play corner and nickel because I've done that my whole career. And just being able to be back there and play safety, it's just another opportunity, letting them see I can play all positions in the secondary."
Marshall signed with the Chargers last August after being released by Miami at the end of training camp. He solidified the cornerback position after high-priced free agent Derek Cox lost his starting job with five games left in the regular season.
Marshall played 603 defensive snaps in the regular season and finished fourth on the team in tackles with 71. He also had six pass defections and a fumble recovery.
A Los Angeles native, Marshall had opportunities to sign elsewhere, but returned to San Diego because of closeness to his family, familiarity with the scheme and a chance at another deep playoff run.
"I like it here," Marshall said. "It's close to home. It's close to my wife and kids. Once we got the call that there was a possibility for me to come back here, she was all for it. She didn't want me to go anywhere else. I didn't want to go anywhere else.
"It felt like it fits me here. I had fun last year playing here and going to the playoffs. That was only my second time going to the playoffs, and I know what type of team we have here. And bringing back a lot of guys that we had last year, with the additions that we had, I know we can get to the playoffs again. It's just the fact of us making the plays that we need to make to get us there."