Richburg played in just four games with the Giants last season because of a concussion, and he wasn't happy when he was placed on injured reserve in early November with nine games remaining. Richburg thought he was on the verge of returning, and he was eventually cleared several weeks later.
He became expendable after former Canadian Football League star Brett Jones played well in his place.
Richburg, 26, was a second-round pick out of Colorado State in 2014 and he missed just one game in his first three professional seasons. He played guard most of his rookie year before taking over the starting center job.
ESPN's Jordan Raanan contributed to this report.