ENGLEWOOD, Colo. -- From the moment the Denver Broncos closed out their 6-10 season in December, linebacker Brandon Marshall has admitted that his future with the team was most certainly in doubt.

Marshall has been notified by the Broncos that they are most likely not going to exercise his option and he will be a free agent on March 13, a source told ESPN's Adam Schefter on Friday.

He acknowledged the news on Twitter and noted ankle and knee injuries that limited him the past two seasons.

Much Love for Broncos country! Still not over yet, but being injured 2 out of the last 3 years after the Super Bowl killed me! But that's life. I'll land on my feet as I always do. ✊🏾 — Brandon Marshall (@BMarshh) February 15, 2019

As the 2018 season drew to a close, Marshall was largely a situational player on passing downs as rookie Josey Jewell had been given more playing time at inside linebacker.

The 29-year-old Marshall played in 11 games last season, starting seven, and finished with 42 tackles without a sack or interception. He has two years remaining on a contract extension signed in 2016, and the Broncos would carry a dead money charge of $4 million against the salary cap when Marshall formally becomes a free agent.

Marshall is currently slated to count $8.843 million against the salary cap in 2019 and $9.5 million against the cap in 2020.

There are still 26 days until free agency formally opens, so there is the slimmest of chances that the Broncos make other decisions and elect to keep Marshall. But for now, he expects to be an unrestricted free agent next month when the new league year begins.

A fixture for his charitable works in both Denver and his hometown of Las Vegas, Marshall recently had hoped he wouldn't get caught up in the Broncos' impending roster makeover after 5-11 and 6-10 finishes over the past two seasons.

"Absolutely I want to finish my career here," Marshall said. "I always said that, always felt that and I've been on record saying that over and over, but you know there's going to be changes here [in Denver]. They're not just going to sit back after the last two years. That's not how they work here. We all know that. But I love it here, I've been in the community a lot. I've won a lot of games here, so I would love to finish my career here.''

Marshall has said he wouldn't get an indication about where he stood with the Broncos until new coach Vic Fangio, who was hired last month, evaluated the roster or when president of football operations/general manager John Elway started to make salary-cap plans.

"You don't know what the new coaches want, what [Fangio] wants," Marshall said. "As a player, you don't control those decisions. I've been injured. We haven't won games. You don't control what they think about. As a player. I just want to get healthy because I know I have a lot of football left in me."

Marshall was the Broncos' Ed Block Courage Award winner and the team's Community Ambassador award winner in 2015. He launched FEEL (Feed & Educate to Empower Leaders) to benefit families in Denver and Las Vegas. He also founded a leadership program -- Williams Marshall Cares Leadership Program -- that has worked with youth in both Denver and Las Vegas.

A former college teammate of Colin Kaepernick at Nevada, Marshall also was among the first group of players who knelt during the national anthem in 2016. He also met with Denver's police chief and police union during that season and donated thousands of dollars to local charities.

Marshall, a fifth-round pick of the Jacksonville Jaguars in 2012, was signed to the Broncos' practice squad in 2013. He quickly showed he could carve out a spot on a defense that went on to be one of the league's best in the Super Bowl run to close out the 2015 season.

In his career, he has 419 tackles, 6.5 sacks, 4 forced fumbles and 2 interceptions.

"I'll never forget the Broncos were the team who believed in me," Marshall said recently. "I was told I wasn't good enough in Jacksonville, that I wouldn't make it. A lot of who I am as a player and as a man has happened in Denver, with the Broncos. I can't predict the future, but I've always tried to stand up for what I believe in, help people and try to be the best player I could. I'll keep doing that."