According to our reader poll, the San Francisco 49ers should now focus on extending the contract of receiver Michael Crabtree.Last week, the 49ers secured quarterback Colin Kaepernick through the 2020 season. We asked readers who they'd like to see signed next: Crabtree, guards Mike Iupati and Alex Boone or tight end Vernon Davis.Crabtree and Iupati are entering the final year of their deals. Davis and Boone have two years left on their contracts but they have stayed away from the voluntary portion of this offseason because they are unhappy with their current contracts.