The team later confirmed the move in its official announcement.
Denver acquired Casey last offseason in a trade from the Titans, who were looking to shed salary. Casey had been a productive player but was hurt for a majority of the 2020 season.
According to Over The Cap, releasing Casey frees up $11.874 million in cap space with no dead money.
Casey, 31, is a former third-round pick of the Titans back in 2011. He still had two years remaining on his five-year, $37.431 million contract when he agreed to a four-year, $60.4 million extension that included $40 million guaranteed back in 2017.
Casey stood to make a base salary of $11.25 million for the 2020 season when he was traded to the Broncos for a seventh-round pick.
In 2020, Casey appeared in three games for the Broncos and recorded 14 tackles, including one for a loss, no sacks and three pass defenses. Pro Football Focus had him rated as the No. 20 interior defensive lineman out of 119 qualifying players.