When it comes to breaking down the defensive numbers, you can make the argument that the Ravens have played better without linebacker Ray Lewis.
In the latest Football Outsiders post by Vince Verhei, he points out that the Ravens have given up 20.3 points, 399 total yards and 137 rushing yards per game. Without Lewis, the Ravens allow significantly fewer total yards (324) and rushing yards (115) per game. Baltimore, however, did allow more points per game without Lewis (22.6).
Even before Lewis tore his triceps in October, the one area where Lewis has been vulnerable is in pass coverage. Andrew Luck and Peyton Manning took advantage of Lewis not being able to keep up with tight ends and running backs in the playoffs, but they didn't expose Lewis enough where he became a liability. If Lewis is going to be used on passing downs, the Ravens need to have him rushing the quarterback because he's much better moving forward at this point in his career.
The numbers support Lewis' struggles in coverage. When Lewis has played this season, opposing running backs have caught 70 percent of the passes thrown their way and averaged 5.6 yards per target. Those numbers are a little lower than the average for running backs. In his absence, though, that catch rate fell to 62 percent, and the average gain to 3.9 yards. This could be a problem against Patriots running backs (Danny Woodhead, Shane Vereen and Stevan Ridley) who have caught a total of 54 passes this season.
Still, the Ravens are better off with Lewis than without him. The numbers that spell that out are wins and losses. The Ravens are 7-1 with Lewis this season and 5-5 without him. Lewis' announcement that he was retiring at the end of the season has inspired the Ravens in these playoffs. That's more of an impact than one tackle, sack or pass deflection can make.