The Broncos already notified Marshall they will not be picking up his option -- which will officially make him a free agent on March 13. Marshall has played in Denver since 2013, where he grew into one of the best LBs in the league.

And, while Brandon's agent is out speaking to other teams (there's most definitely interest in the 29-year-old) ... Marshall says there's no bad blood with Denver and he could see a situation where he's back in orange in 2019.

"I wouldn't rule out a return yet," Marshall says ... "Still a chance I could return to the team. It could definitely happen."

Marshall not only lives in the Denver area, but he's also heavily involved in the local community and considers Denver home.

But, for a return to Denver to make sense, it has to make dollars.

"If things work its way out, I'm definitely open to a return ... they have to be open as well, we'll see."

Marshall was limited to 11 games in 2018 due to a knee injury -- but still logged 42 tackles.

He has the most solo tackles of any Broncos player since 2013. Over the course of his career, Marshall has 419 tackles, 6.5 sacks, 4 forced fumbles and 2 interceptions.

He also has a Super Bowl ring from the Broncos victory over the Carolina Panthers in Super Bowl 50.