To say that Rayford has been around the block a little bit would be an understatement. He has a resume that reads a bit similarly to that of Tom Johnson, who the Vikings signed in free agency last year. Rayford started his career in 2008 (after going undrafted out of the University of Washington) with the B.C. Lions of the Canadian Football League, and then moved on to the Arena Football League with the Spokane Shock (2009) and the Utah Blaze (2010-2013).
In 2013, he finally made it to the National Football League with the Indianapolis Colts, where he spent Training Camp, and then moved on to the Dallas Cowboys just before the start of the regular season. He ended the 2013 season on the Cowboys' practice squad, and was released before the 2014 season. He then went back to the Canadian Football League with the Calgary Stampeders (for all of three days) and the Montreal Alouettes. Finally, he found himself back in the Arena League after being selected by the Jacksonville Sharks in that league's dispersal draft.
Rayford was one of the players that participated in the Veterans Combine in late March. That means that three players from that event have found NFL jobs, and two of them (Rayford and quarterback Mike Kafka) have been signed by Minnesota.
The 6'7", 265-pound Rayford will get an opportunity with the Vikings. With the Vikings being as deep as they are on the defensive line, I'm not sure how much of a chance he has of sticking, but he's on the team for right now.