5. Marc Trestman
There was optimism when Marc Trestman came into Baltimore. He had an unsuccessful tenure as the Bears head coach, but was a solid offensive coordinator.
You can argue that Trestman did not get a fair shot in 2015, because of the number of injuries the Ravens suffered. Even with the injuries, the Ravens finished the season with one of the better ranked offenses in the league. Many fans thought that Trestman should have been fired following the season, but he was given one more shot.
The next season did not last long. The Ravens started out the season 3-1, but the record was deceiving. The offense struggled to score points and it took lucky breaks to pull out wins. After a week five loss to the Redskins, the front office had seen enough and fired Trestman. It was an unsuccessful tenure and the Ravens were not able to find any balance in their offense.