Achilles tendon rupture
Allen was drafted by the Philadelphia Eagles in the second round (37th overall) in the 2010 NFL Draft. The Eagles traded quarterback Donovan McNabb to the Washington Redskins in exchange for the pick used to select Allen. After Marlin Jackson suffered an Achilles tendon rupture during organized team activities, Allen was named the starting free safety going into training camp, replacing the 2009 starter, Sean Jones. Allen was signed to a four-year contract on July 27, 2010.