On offense the NFL range for 3rd down percentage is 49% (Colts) to 25% (Raiders). The Pats rank 13th at 41% (68/165) - ironically, just ahead of Pittsburgh.
On defense the range is from 30% (Ravens) to 49% (
Colts - funny that they're best and worst in this category). The Pats rank 29th (67/150) with 45%, better than only the Bengals, Chiefs and Colts.
The inability to convert third down on offense against the Steelers was an anomaly. The point about the Pats not being able to make stops on third down, which has been brought up on multiple threads, is a fact - and a huge concern that is in need of being addressed this off-season.
NFL Stats