<P> The New England Patriots generally run a modified Erhardt - Perkins offensive system and a Fairbanks - Bullough 3--4 defensive system, though they have also used a 4--3 defense and increased their use of the nickel defense . </P> <P> The Patriots run a modified "Ron Erhardt - Ray Perkins" offensive system installed by Charlie Weis under Bill Belichick . Both Ron Erhardt and Ray Perkins served as offensive assistant coaches under the defensive minded Chuck Fairbanks while he was head coach of the Patriots in the 1970s . This system is noted for its multiple formation and personnel grouping variations on a core number of base plays . Under this system, each formation and each play are separately numbered . Additional word descriptions further modify each play (see below for examples). </P> <P> The Erhardt - Perkins system traditionally had a reputation (whether or not earned) of being a traditional smash mouth offense that maximizes a team's time of possession and does not as frequently call upon its running backs to serve as receivers . Erhardt was famous for his adage, "throw to score, run to win ." This may have been especially true during the years Bill Parcells ran this system as the head coach of the New York Giants . This system was thought to be particularly well suited for teams playing in harsh outdoor weather conditions of the northeast of the United States . </P>

What kind of offense does bill belichick run
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