Greenwood was drafted in the fifth round of the 2012 NFL Draft (#148 overall) by the Detroit Lions. He played his college ball at Division III Albion College in Michigan. He has played for both the Lions and the Dallas Cowboys over the course of his career. He was with the Lions again during training camp this year, but was released on the final cutdown day by Detroit.
Personally, I had thought that the final spot on the practice squad was earmarked for offensive lineman Austin Wentworth, who had initially made the 53-man roster but was released on Sunday after the Vikings made a couple of waiver claims. However, it appears that the Vikings had other ideas, as Greenwood is the last name on the practice squad for Minnesota.