The NFL's rugby invasion continued when the Detroit Lions signed Carlin Isles. NFL teams have kicked the tires on rugby stars before, but none have become stars or starters on the pro level yet. However, Isles was once dubbed the fastest rugby player in the world and is a unique athlete for any sport. At his workout for the Lions this week, Isles reportedly ran a blistering 4.22 40 yard dash. Lions coach Jim Schwartz, who may be coaching his final game on Sunday, put the signing in perspective.

"You're looking for athletes," Lions coach Jim Schwartz said. "It hasn't been unusual to see basketball players transition to the NFL, and it's not just recently; that goes way back.

"Even track guys like Bob Hayes and Renaldo Nehemiah -- things like that. An athlete's an athlete, and there are skills you can develop, and if you see something that you like, then you can work with him."

On the downside, the 24-year-old Isles is just 5-8 and 166 pounds and hasn't played football in four years. In 2016, Isles will either be playing for the United States' first Olympic rugby team or playing in the NFL.