We examine the exact relation between the superconformal symmetry breaking chiral superfield ( X) and the goldstino superfield in microscopic models of an arbitrary Kahler potential ( K) and in the presence of matter fields. We investigate the decoupling of the massive sgoldstino and scalar matter fields and the offshell/onshell-SUSY expressions of their superfields in terms of the fermions composites. For general K of two superfields, we study the properties of the superfield X after integrating out these scalar fields, to show that in the infrared it satisfies (offshell) the condition X 3 = 0 and X 2 ≠ 0 . We then compare our results to those of the well-known method of constrained superfields discussed in the literature, based on the conjecture X 2 = 0 . Our results can be used in applications, to couple offshell the (s)goldstino fields to realistic models such as the MSSM.