Friday's move will save $11 million in cap space, but it leaves the Browns with a huge hole in the middle of their defensive line. Richardson's contract had no guaranteed money remaining.
He signed with the Browns on a three-year deal before the 2019 season, starting 31 games and getting 7.5 sacks over two seasons.
This offseason, the Browns signed Malik Jackson to compete for a starting job at defensive tackle. They also have defensive tackle Andrew Billings joining the team after he opted out of last season due to the COVID-19 pandemic.
Cleveland signed Clowney on Thursday to a one-year deal worth up to $10 million.