Nixon's BABIP is somewhere north of .380. In contrast, his career BABIP is .310.
His average is bound to fall. Which will take his OBP, OPS, and SLG% with it. He might OPS around .800 - .820, which is terrific value for $3 million.
Jacobs Field is also aiding Trot Nixon as well. The Jake tends to inflate LH Avg by 10%, and boosts HR rates by about that same figure.
Fenway tends to inflate average by about 8%, but deflate LH power by about 15%.