The Ravens began their 2008 campaign at home against their toughest AFC North foe, the Cincinnati Bengals.  In the first quarter, Baltimore opened the scoring with WR Mark Clayton scoring on a 42-yard TD run from a double-reverse play.  In the second quarter, the Ravens increased their advantage with Matt Stover kicking a 21-yard field goal.  The Bengals responded with Shayne Graham kicking a 43-yard field goal to end the first half.  In the third quarter, Baltimore responded with rookie quarterback Joe Flacco scoring on a 38-yard TD run.  In the fourth quarter, Cincinnati tried to rally as CB Johnathan Joseph returned a fumble 65 yards for a touchdown.  Ultimately, the Ravens defense stopped a potential Bengals scoring drive on fourth down late in the fourth quarter and won the game. Joe Flacco in his rookie debut, completed 15 of 29 passes for 129 yards (along with a touchdown run).. How many incomplete passes did Flacco have?