Lynch, who did not play in the game, sat on an orange cooler, arms on his knees, while all others around him stood.
"On Marshawn, talked to Marshawn trying to make sure we're on the same page," Del Rio said. "He said, 'This is something I've done for 11 years. It's not a form of anything other than me being myself.' I said, 'So you understand how I feel, I very strongly believe in standing for the national anthem. But I'm going to respect you as a man, you do your thing. We'll do ours.' It's a non-issue for me."
Del Rio told reporters he did not believe Lynch sitting would be a distraction.
NFL Network's Michael Robinson, who was Lynch's teammate in Seattle for close to four years, did not interpret Lynch's sitting as a form of protest, explaining to NFL.com that Lynch has rarely stood for the national anthem during his career.
Lynch's locker was cleared by the time the media was permitted in the postgame locker room Saturday night, per multiple reporters.
Lynch rarely talks to the media but has voiced his support for quarterback Colin Kaepernick's 2016 season-long decision to kneel during the anthem to draw attention to what he saw as incidents of police brutality against people of color.
Kaepernick remains an unsigned free agent.
The Associated Press contributed to this report