Sacks are the most useless statistic to judge a defense. There've been teams, and in some cases even players getting 3,4,5,7, 8,9 sacks in one game, and nothing for next many games.
Its about bringing pressure. Negative plays are result of pressure ! And sack is one type of negative play resulting from pressure, as are forced int, incompletions, QB strips/fumble etc. Of all the teams, Pats should know that very well considering what happened to our OL in some SB's losses...Bears, Packers, G-men, and then following year in Rd 1 vs Ravens. On the other hand when our team handled the pressure from Panthers and Eagles vaunted Defensive front, or likes of "Lights Out" clown in SD we were SB champs, or moved deeper into playoffs.