‘Castillo, 59, joined the Bills coaching staff in 2017 and also served as the team’s run game coordinator. Buffalo’s offensive line struggled this season after losing Richie Incognito and Eric Wood to retirement in the offseason. Without their two Pro Bowl linemen, Buffalo’s line failed to create running lanes and struggled in pass protection. Although Castillo cannot be faulted for the circumstances that led to Incognito and Wood retiring, Buffalo’s line never gelled or showed signs of improvement in 2018.’