Manager Steve Coppell has resigned as manager of Bristol City just five days after the first game of the season, a home defeat against Millwall. Managers come, managers go, that's the nature of football, but it is always something of a shock when the first change of the season comes so soon after the big kick off.Last year, Norwich, then in League One, dispensed with manager Bryan Gunn after an opening day hammering against Colchester, replacing him with the Colchester boss Paul Lambert. However, this one is all of Coppell's own making.Not for the first time he's left a club after just a short space of time. He joined Bristol City in April but only took over the team after the 2009/10 season had ended, but he's admitted he couldn't get passionate about the role and has not only resigned but announced his retirement from football management.He said: "It is with the deepest regret that I confirm my departure from Bristol City. I have made my decision after very careful consideration and I believe that it is in the best interests of both the club and me personally that we go our seperate ways."It has become clear over recent weeks, that I found I could not, for whatever reason, become passionate about the role and give the commitment the position demands."I appreciate that the timing of my departure is not ideal, but I believe it is best for the club to appoint a new manager or indeed appoint Keith Millen, who has a deep knowledge of the club and the squad, a this stage of the season."Bristol City later confirmed that Keith Millen had been appointed as the club's new manager and has signed a three year deal to replace Coppell.