Former Detroit Lions running back Jahvid Best runs in the eighth spot of the 100-m sprint preliminary that Usain Bolt won. Right, Best with the ball against the San Francisco 49ers in 2011. (AP Photos Morry Gash, Rick Ostenoski).

As a former NFL player, Jahvid Best has competed against some of the most talented athletes in the world. On Saturday, he took on the fastest man in the world in the Rio Olympics.

Best left the NFL after three concussion-plagued seasons with the Detroit Lions. He still possessed world-class speed, so he tried his hand at sprinting and qualified for the Olympics for St. Lucia, his father's home country.

He was in the same heat Saturday as Usain Bolt, who won the 100-meter sprint with a time of 10.07. Best was a distant seventh with 10.39 seconds, not good enough to qualify for the next round.

Best played football at Cal and was one of the nation's most dominating running backs. He was chosen in the first round of the NFL draft in 2010 and once had an 88-yard touchdown run against the Bears on Monday night.  Concussions derailed his career.