Dec 3, 2007: New England 27, Baltimore 24. Patriots were favored by 19.5.
October 4, 2009: New England 27, Baltimore 21. Patriots were favored by 2.
January 10, 2010: Baltimore 33, New England 14. Patriots were favored by 3.5.*
October 17, 2010: New England 23, Baltimore 20. Patriots were favored by 3.
January 22, 2012: New England 23, Baltimore 20. Patriots were favored by 7.
September 23, 2012: Baltimore 31, New England 30. Ravens were favored by 2.5.
So the Patriots have covered the spread just twice in the last six meetings with the Ravens, and once, this year, was when New England was an underdog.
What does this mean? Nothing, of course. The 2012/2013 Ravens have not been a juggernaut on defense, and beat a rookie QB in the first round and got lucky as hell to beat Peyton Manning on the road in the second round.
* Playoff game. The one where Ray Rice took one to the house on the first play of the game.
** AFC Championship game.