The San Francisco 49ers' workout with free-agent receiver Austin Collie comes as the team moves forward without injured starter Michael Crabtree.2009-11 Crabtree vs. CollieCollie, 27, has his own concerns. Knee surgery forced him to miss the 2012 season. He also has a history of concussions.The chart shows Collie and Crabtree producing at about the same level over the same number of games across the 2009 through 2011 seasons. Collie was with Indianapolis and catching passes from Peyton Manning during those years.