Why not? They held Philip Rivers (6th in passing yards), Tony Romo (7th in passing yards), Eli Manning (4th in passing yards right behind Rodgers), and Roethlisberger (9th in passing yards) to under 400 yards. In fact, the only two QBs who got 400 yards or more were Chad Henne and Vince Young and both of those games were blow outs and the they got most of their yards in garbage time.
It is possible that Rodgers could throw for 400 yards, but the only time the Pats allow a 400 yard passer is when the game is over early in the 4th quarter and the defense gets laxed.
There isn't a magical entity that has teams taking their foot off the gas in blow outs. It is a fairly common occurrence actually. The problem is that the Pats are consistently blowing out teams this year. It isn't a coincidence that the three highest scoring offenses are #32 (Patriots), #31 (Packers), and #27 (Saints) in yards allowed this year.
Lastly, the man-to-man stuff was experimentation this past weekend. It was the first time they used it more than a play here and there since about week #3.