<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>

What kind of offense does the patriots run