According to Chris Mortensen, the NFL has found that the Patriots underinflated 11 of their 12 allotted game balls by two pounds on Sunday. This is a significant difference, as league rules stipulate inflation to 12.5-13.5 PSI.
To put that in perspective: for a tire to deflate by 15% on its own, there would need to be a 75-degree drop in temperature. Obviously, nothing like that occurred at Foxboro on Sunday.
The league's (surely reluctant) investigation was prompted by D'Qwell Jackson's second-quarter interception of Tom Brady. A member of Indy's equipment staff noticed the discrepancy and ran the news up the flagpole, to head coach Chuck Pagano and GM Ryan Grigson.
Per Jason La Canfora, some Ravens think the kicking balls were underinflated during New England's 35-31 divisional round win.
2011 comments from Brady about a preference for "deflated balls" take on a new light today. Of course, it's far from the first rules-related scandal to tarnish the Patriots and Bill Belichick's reputation.