Will Johnson, Ellington allow 49ers to let Crabtree go?

Daily 49ers blog for NBC Bay Area website: Trade for Stevie Johnson and draft of Bruce Ellington gives 49ers a more complete group of receivers, and could allow 49ers to let Crabtree walk after contract expires in 2014. http://www.nbcbayarea.com/news/sports/Crabtree-Iupati-Futures-With-49ers-Now-More-Cloudy-259390141.html