Williams was great in the minors with San Fran a few years ago. Injuries, suspensions, etc. have hindered his development through the Giants organization, Cubs organization and Athletics organization. On the Nationals he is pretty much guranteed a rotation spot and at only age 25, he still may have something left in the tank.
Not worth a look in 10, 12 or most 14 team leagues, but in 16, 18, 20 and larger leagues he could be worth a last round flier.