The story of Casey is an interesting one. I've always been a big fan of players who are versatile on offense (i.e. remember MarQueis Gray over the past two training camps?). Casey played for the Houston Texans from 2009-2012. His best season came in 2012, when he caught 34 passes for 330 yards and 1 touchdowns. He was an H-Back, running back, fullback, tight end, and wide receiver all wrapped into one.
When the Philadelphia Eagles gave him a 3-year deal worth $14.3 million at the start of the 2013 season, I envisioned them having big plans for him in Chip Kelly's offense. Instead, they barely utilized him as a receiver, as he logged 6 catches for 90 yards and 2 touchdowns in two years.
Casey it a hot player on the free agent circuit right now -- that's a benefit of being released prior to the end of your contract. At 6-3, 240 pounds, I would label Casey as being a somewhat similar player to FB Marcel Reece of the Oakland Raiders. Reece carries the ball more than Casey ever has, but he's been a versatile piece in Oakland's offense since 2010. The Browns' new offensive coordinator, John DeFilippo, was the Raiders' quarterbacks coach from 2012-2014, so if he liked how Reece was utilized there, he might envision a similar role for a guy like Casey in Cleveland.