The Patriots averaged 6.0 yards per play when Rob Gronkowski was on the field this season, compared to 5.4 when he was off of it.
Further, Tom Brady's completion percentage fell from 65.7 to 58.4 when Gronk wasn't on the field. The Pats boasted a 23:3 TD:INT ratio on snaps Gronk played, compared to 11:6 without him. Those numbers include four pass attempts, and one interception, from Ryan Mallett. Of course, the Patriots went 4-1 without Gronk in the regular season, but his absence is going to very much be a major factor in Sunday's AFC title game.