Derrius Guice, Washington’s rookie running back, tore his ACL during the preseason. Over 90 percent of NFL athletes who tear their ACL are able to return to their previous level of play. In fact, these days, it’s almost assumed that will happen without fail. When that doesn’t occur in a timely fashion, it’s usually due to other associated injuries, such as meniscal tears, injuries to a second ligament, cartilage damage, etc. Some, such as Dalvin Cook, return only to be hampered by hamstring injuries that their previous knee injury probably predisposed them to.