Grigsby turned pro in 1988 and lost his second professional fight, to flyweight legend
Michael Carbajal who was making his professional debut. In 1998 he captured the vacant IBF light flyweight title by decisioning
Ratanapol Sor Vorapin. He defended the belt once before losing it to
Ricardo Lopez in 1999. In 2000 he captured the WBO light flyweight title with a decision win over
Nelson Dieppa, but was stripped of the belt after the fight for testing positive for marijuana. The fight changed to no decision. He fought sporadically before capturing the IBF light flyweight title with a decision over
Victor Burgos in 2005. He lost the belt in his first defense to
Ulises Solís, and lost a rematch with Solís in 2007. ==Professional boxing record==