The most overrated Baltimore Raven of all-time is Anquan Boldin.
Before all your senses are drowned in outrage, take a second and think about it. Boldin's best and most memorable moments came in the 2012 post season. The problem is not related to Boldin being an overrated player, when talking about his skills, but more so when related to the insane amount of backlash when the Ravens traded him.
The fanbase lost it's mind. Outsiders thought the front office had gone crazy. Anquan Boldin was not Calvin Johnson though, but you would have thought so judging by the fans' reactions. Anquan Boldin did not make Joe Flacco, as so many would like to believe. In the biggest game of the Ravens playoff run, in Denver, Boldin posted a line of 6 receptions for 71 yards. Not exactly otherworldly. Joe Flacco himself was the true MVP of that game. While his two touchdowns against the Patriots stand out, he hauled in 5 receptions for 60 yards. In the entire run, Boldin did not catch over 6 balls.
In prior regular seasons, Boldin never gained 1000 yards and was not incredibly consistent from week to week. He would have huge games where he helped carry the offense on his back only to be mediocre or be shut out completely for weeks at a time. In 2011, he burned Houston for 132 yards on 8 catches. The following week against Jacksonville, he was rather tame, catching 4 for 40.
Boldin was a good receiver. But one could argue he wasn't the best receiver in the franchise's short history. I would personally give that honor to Derrick Mason. Boldin was not as great as the masses thought and after the trade and the subsequent 8-8 season, it was easy to scapegoat the front office. The reaction to the trade was in no way congruent to the caliber of player Boldin was, and that what makes him overrated.