Martin later released a statement:
Adam Caplan of Sirius XM noted the move will save the Bucs $6.75 million in salary-cap space.
Martin, 29, was under contract through 2020 before his release. Now he'll become a free agent.
The Boise State product missed the first three games of the 2017 season while he served the remaining portion of a four-game suspension levied in December 2016.
He ended up rushing for 406 yards on 138 carries with three touchdowns in 11 appearances. It marked the second straight year he averaged a lackluster 2.9 yards per carry (he did so over eight games in 2016).
Bucs general manager Jason Licht said last month that Martin's inability to make plays after his return from suspension was the main reason for the team's rushing struggles.
"I think the lack of, or having a hard time getting the run game going was...you know, Doug just didn't have...he just wasn't ever the same," he said, per Rick Stroud of the Tampa Bay Times. "And it wasn't until late that Peyton [Barber] kind of arrived and things started going a little bit better with him, starting with the Green Bay game and on and on."
Pro Football Focus graded him as the league's No. 53 running back for the 2017 campaign.
While Barber did show signs of promise down the stretch, including 102 rushing yards against the Packers in early December, Tampa will likely be in the market for another back either in the draft or free agency.
Meanwhile, Martin has a pair of 1,400-yard rushing seasons on his resume (2012 and 2015) but will probably be forced to take a short-term, incentive-laden contract on the open market because of his age and lack of production over the last couple of years.