NFL, and they were dating back as far as 2011. Raiders special teams and assistant head coach Rich Bisaccia will takeover the reigns on an interim basis to cover for Gruden.His resignation comes in the fourth year of a 10-year contract worth around £7.4million.In a statement released on Monday night, Gruden apologised for his comments and stated his intention to leave.“I have resigned as head coach of the Las Vegas Raiders," he said in a statement.