Tony Mandarich
NFL scouts thought that Mandarich was the best offensive tackle prospect ever. He had an outstanding career with Michigan State but they didn’t know he was abusing steroids. Mandarich also infamously had an addiction to painkillers and this severely damaged his career. The Packers made him the second overall pick in 1989 ahead of Deion Sanders and Derrick Thomas.

This proved to be a shocking mistake because Mandarich didn’t deliver. He spent four seasons with the franchise before they lost patience and cut him. It was a major disappointment because he arrived with so much hype. There’s no guarantee that any draft picks will succeed but Mandarich crushed the fans (via BVM Sports).